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DIY LED Moonlight Guide

Discussion in 'Freshwater Equipment, Products, & DIY' started by AcydFlames, Oct 13, 2008.

  1. AcydFlames

    AcydFlames Ideas Guy... Sometimes

    Sep 23, 2008
    Likes Received:

    DIY LED Moonlight Guide
    My guide to a simple, reliable, (and best of all for me) relatively cheap aquarium moonlight setup.
    By Adam C.
    Project Completion Time: Approx. 2 Hours (after you spend an hour reading this)
    Project Skill Level: 6/10


    Sit back and relax.

    This is a LONG guide, and will probably seem sporadic at first; so there’s my warning. It’s hard to format a guide in a linear format when there are so many dynamic choices you have to make up front, and every choice affect everything else. It would be best if you could sit back and read ALL of it before you went out soldering connections. And if you make it through, I’m sure you’ll agree that the end results are worth it!

    Disclaimer: It seems now a days you need to disclaim almost everything you tell people about. So on that note, please be aware that everything contained within this guide is only the wisdom and direction of one guy. I am not a professional electrician or professional aquarist, and do not claim to be either in any way. The following info is what I’ve found to work nicely for ME, and might not work either partially or in whole for YOU. Be advised that when playing with electricity, especially around water, you could kill yourself, simple as that. Muster up a fair amount of common sense before attempting anything below!

    Up front, I’ll say that I’ve only done this project on your standard, aquarium “kit” style generic hood (that come with your Aqueon or TopFin type tank kits; the ones like pictured below).


    These simple style hoods offer a clean position for these lights to be installed, and have plenty of room on the inside to hide all of your wiring. I’ve completed three hoods at the time of writing (a 4 LED 29g hood setup, a 2 LED 29g hood, and a single LED 10g hood), and am working on my forth; all have been an extremely similar setup. If you have something other than this style hood, this guide can still be very relevant, but you might have to tweak the setup to fit your needs more than others.

    Now if I didn’t scare you off, rest assured that this is not a complicated setup. This is a simple solution to achieve a specific result. I’m not in the business of reef tanks, or interested in prompting my fish to mate (or any other reason moonlight kits are used to replicate nature); I simply wanted a nice, subtle effect on my new 29-gallon tank. I began researching moonlights only to find that I couldn’t find everything I needed within short reach. It took me a good couple days of reading all kinds of info, from color wavelengths, to fish sleep cycles, and basic electronics (the fun math equation stuff) to finally understand everything. The lack of a single, consolidated source of information on this topic got me thinking that someone should really put an “everything in one place” guide together. So, with that intention in mind, I will try to touch on all aspects, and I will try to explain everything the best I can so that you might adapt this info for your particular needs.

    My choice in the beginning was whether to use LEDs or Cold Cathode lighting. I was almost set on Cold Cathode, and I changed my mind back and forth a couple times. In defense of the Cold Cathode setup, it’s pretty cost effective, has a diffused light by nature, and it a really simple setup (minimal wiring needed to make it work in this case). I settled on LEDs because the run with almost zero heat, and draw an almost negligible amount of power. Cold Cathodes can get reasonably hot, and use an inverter that can generate an excess of 650V to power. I don’t want to start a Cold Cathode vs. LED debate, but in my case, LEDs seemed more appropriate. And I would be willing to bet that most people will have to admit that either lighting setup will produce quite similar results in the end.

    How to get an LED to fire up!
    [Warning: this is the boring technical math stuff.]

    This is probably pretty close to what your LEDs will look like:


    You’ll notice you have two leads on a normal, single color LED: a longer anode (positive lead) and a shorter cathode (negative lead). It is important to remember which is which, as if it is connected backwards, it won’t light up. Also note the flat side in the figure, as the lead toward the flat side will most often be the cathode (negative) side.

    You can of course do your own LED homework, but for our needs, all you have to know for now is that the positive wire from your power source gets connected to the long leg, and the negative wire goes to the short leg. Simple, yes?

    Maybe not. We should take a quick second to talk about how LEDs work. It’s not as simple as connecting the light to a power source, like you do with an incandescent, to get it to light up, but it’s not too much more complicated. The biggest difference is that you need a resistor to help limit the flow of current so you don’t blow the LED up. If you connected the light without the resistor, the LED would light up extremely bright for a matter of seconds, and then burn out, completely destroying the diode.


    Long story short, LEDs offer almost no resistance to the circuit, and they will essentially keep taking in current until the burn out. To solve this problem, you simply add a current limiting resistor in, and like magic, your lights don’t burn out. They turn on, stay on, and live a happy life of 50,000 hours or so. Drive them too hard, and they’re life is shortened, pretty simple. Figuring out which resistor(s) to use is where your LED’s specs come into play.

    When you pick out your LEDs, make note of the technical data associated with it. Specifically, we need to know the Forward Voltage (VF), and the Forward Current (IF).

    Once you know the LED’s specific data, we just use Ohm’s Law to find our value for our resistor.

    Ohm’s Law: Voltage = Current x Resistance (V=IR)

    But we need to find Resistance, so if we solve for the Resistance, we get: R=V/I. And in our case, we’ll use R=(VS-VL)/I

    VS = is our source voltage
    VL = is out LED voltage
    I = the LED current in Amps (usually 20mA, or 0.020A)

    For example, in my case, I wired my LEDs up using the following numbers: LED voltage drop = 3.1V, Current = 20mA, Source Voltage of 13V, with a total of 4 lights.

    To make a quick technical note, the lights in this setup are wired in series, as opposed to parallel. A good LED circuit should always be wired in series. If wired in parallel, the slight differences in the LEDs will cause some to shine brighter, others dimmer, and could possibly keep some from lighting at all. In our case with a small quantity of lights of the same color, either setup would produce almost identical results. But for the sake of it being a “clean and correct” circuit, we’ll wire in series.

    The main difference for our calculations is that in a series circuit, you add the number of volts each LED uses, but the current (mA) stays the same. In parallel, it’s the opposite; the volts stay the same, and you add the current values together. For example, if you had a red LED that ran 1.5V @ 20mA, and you wanted to wire 3 together, your power requirements would depend on if they were wired in series or in parallel. In series, you would add the volts, and not the amps, so you would need 4.5V and 20mA to run that circuit. On the flip side, if wired in parallel, you would need 1.5V and 60mA. This is all another subject that is worth looking into, but we won’t dive in too deep in this guide.

    Plug in the numbers: R = (13-12.4) / 0.020, R = 30 Ohms (if you use the calculator below, these number spit out a resistor value of 33 Ohms, the next highest resistor value). So I used a 47 Ohm resistor, the closest one I had (always use the next highest value, not a smaller one). And also, you have to note the Wattage of the resistors. In my situation, 1/4 Watt were plenty, but if you have higher voltage, or fewer LEDs, than you might need 1/2 Watt or higher. Basically, the higher the amount of power you have to absorb, the larger the resistor needs to be. For example, if you’re trying to run a single LED off a 12V source, than you’ll need at least a 1/2 Watt resistor to be safe. When in doubt, go BIGGER. There are no problems with larger resistors, you only run into problems if they’re too small.

    You can use your numbers in the formula above, and do your own math, but why? There are numerous LED calculators online, just Google “LED calculator”, and use any you choose. I suggest the on in the Links section at the end. It’s what I used, I like it. I found myself going to this one most often, since it calculated series/parallel combos, and gave recommended resistor Watt ratings. Technically, they should all give you the same answers regardless of which calculator you choose, but maybe check a couple to be sure (sometimes programmers are shady fellows).

    Once we have all of our numbers ready, write them down for later.

    Assembling your troops.

    Let’s start with what you’ll need. I guess that if you had absolutely nothing on hand, then this could be an expensive project. But I’d like to assume that you could gather a lot of the parts and tools you’ll need from around the house. Here is the total list of stuff that you’ll need to complete this project. The items listed as optional are just that, but they do tend to make things cleaner and easier at the end of the day.


    The LEDs
    Power Adapter (or batteries; details below)
    LED holders (optional)
    Toggle Switch (optional)
    Heat Shrink (optional)
    Electrical Tape (in the case of no heat shrink)

    Utility Knife
    Multimeter (recommended; semi-optional?)
    Wire Strippers (optional)
    Soldering Iron (optional)
    Solder (if you’ve got an iron of course)
    Drill w/Drill Bits (optional)
    IC Breadboard (optional)
    Helping Hands (optional)

    The Juice
    I’m going to go a little out of order here, and start with what was most important for me, my power supply. This will determine how many lights you can run, and how bright. For me, since I was going to keep these things running for at least 4+ hours a night, I figured a power adapter was my best option (aka an AC/DC transformer, wall wart, power brick, etc. See Fig C-2). If you only plan to run them when you want to view your tank (i.e. short intervals, only a few minutes at a time to impress your friends), than a battery setup might work just as well for you. The wiring and math is all the same, it doesn’t matter where you get your power from, just how much of it you’re getting.

    Adapting A Power Adapter


    If you plan on going with a battery setup, you should probably still read though this section, just to help understand everything; as opposed to skipping down to “Battery Power”

    If you want endless power, with no batteries to ever change or slowly die out on you, than a power adapter is what you’ll need to find. You can buy these things, but most people will find that they have quite a few laying in the bottom of their junk drawer, if you go looking for them. Think of things like old cell phone chargers or old digital camera plugs. I bet you’d be surprised at what you can find.

    I went digging through some old stuff and came up with a perfect power supply for my needs. If you read all of that small print on a power adapter (you know, that stuff we all ignore and just plug it in anyways), you’ll see the key numbers we’re looking for. The “Input” should be a pretty standard 110VAC (in the US at least, higher of course if you’re over the pond). The “Output” is what we need to look at. We need to know the Output Voltage and Current.

    The first thing you should check is that the “Output” is DC (i.e. 12VDC). If it says AC (i.e. 12VAC) than it’s no good for us. LEDs need DC current to run (for the most part, but that’s a different project all together). Once you find a DC adapter, continue reading the other numbers.

    Second, we need to find a suitable voltage. You’ll have to think about how many lights you want to run in your tank (see below in “The LEDs” section for more about the light angles and quantities). More lights will mean a brighter setup; I wanted somewhat dim, but overall coverage. The choice is your. Once you know how many lights you will want, and their Forward Voltage (again, see below for details), you’ll know what you need from your power adapter.

    In my setup, I used 4 lights, rated at 2.8-3.4V. I set them up for 3.1V. You need to take the Forward Voltage of the LEDs and add them all together (since we’re wiring in series). For me, 4 LEDs @ 3.1V = 12.4V. Then you need to find a power supply that will deliver at least that much voltage.

    A funny thing about power adapters is that they’re “rated” for a specific value under a specific load. Since our LEDs will be an extremely light load (they draw very little power), the power adapter will never reach that “rated” load. Long story short, all this means is that since the load is so light, the power adapter will actually be outputting MORE than it’s rated for. This isn’t a bad thing, but be aware.

    This is where that multimeter comes into play. If you plugged your power adapter into the wall, and took a reading on the voltage it was outputting (with zero load), you’d probably be surprised at how much higher the value was. For example, my power adapter is rated for 9VDC, but when I plugged it in, I got 13V! This worked great for me, since I was originally thinking I could only use 3 lights (3 LEDs @ 3.0V each), but now this gave me the option to use 4.

    The second value listed under “Output” on the adapter will be the Current. For this setup, we really only need an adapter rated at maybe about 30mA (but good luck finding one rated that low!) Any value higher than 30mA will do just fine. The Current is how much power the circuit draws, and the circuit will only draw what it needs. So if your adapter is rated for, lets say 100mA (like mine was), that’s fine. It will only draw its needed current. If your adapter was rated at 1000mA (or 1 Amp), again, it would work, our circuit will still only draw out 20mA (or whatever we set it up for. Also see “Aftermath: Tweak #2”).

    If given the choice, I would suggest using the closest (smallest) value adapter that fits your needs. It will often times mean a smaller, lighter power adapter, and mean that our resistor values will be lower. My adapter was rated for 9VDC @ 100mA, and in reality, output 13VDC. I was going to use 4 lights @ 12.4V total, so 13V is about as close as you can get!

    Battery Power - Using Canned Energy


    1. 2xAAA battery pack powering a single LED setup.
    2. 4xAA battery pack powering a 2 LED setup.

    A battery pack can serve as a viable option when thinking about what you want to power everything with. Batteries are cheap enough, them eliminate the need to find/buy a suitable power adapter, and are a little less intimidating to use for some folks.

    The downside? Batteries die; the wall outlet doesn’t. Your light output will also diminish as the batteries wear down over time. But if you don’t plan on this being a constant daily feature of your aquarium though, than this could all work perfect for you.

    First, just like with the power adapter method, you have to get the right power source. Basically, you just need to figure out how many batteries you need to power up your specific lights. If you only wanted to run 2 wide angle LEDs for your moonlights, than a set of 4 AA batteries would work well for you (1AA = 1.5V, 4AA = 6V), and should still last you a good long time between battery changes. If you want more lights, you need more power. 9V batteries can be great for a project like this, with a good voltage and decent capacity.

    But again, just like with the power adapter, try to come close to matching your LED requirements with your source or power. No need to run a pair of 9Vs to power up those 3 lights.

    Batteries also have one extra super advantage. They have built-in resistance! You could hook up an LED directly to the battery, and since it has its own resistance, it won’t burn your diode out! So if you match your supply voltage to your LED requirements perfect, you can get away with not using any resistors! (But you still might want too, that’s what “Aftermath Tweak #2” is all about). Avoiding resistors is not my recommendation though, but I thought I’d at least note that it’s possible; if you ditch the resistors, be aware that you can still fry your LEDs rather easily.

    The LEDs:
    These are of course the most important part of your setup; it’s what you’re reading this for after all. LEDs come in almost any color you can imagine, with various sizes, intensities and shapes. What we’re after here is a pretty standard size of 5mm, and of course, blue in color. This guide could easily be modified to used any color or size of LED, assuming that you know all of the specifics of that LED.

    I purchased my LEDs from Unique-LEDs.com. They seemed to have the best combination of selection, price and technical data that I was looking for. Feel free to get yours from anywhere you’d like. The only thing we’ll need to know to power them up is the Forward Voltage of the LED (changes and depends on the color, size and intensity) and normal Operating Current (20mA is pretty common). Most online stores will list this data somewhere on their site. Unique-LEDs lists it both on the page detailing the light, as well as a downloadable PDF with more technical data than you’ll ever need (for a lot of the LEDs, but not all).

    When it comes to the blue LEDs, there are a handful of different wavelengths available. If you’ve read through other guides, you’ll know that everyone has their own “perfect” wavelength. Everyone is trying to simulate natural light. For me, that wasn’t as important. I wanted to come close, but really, you’re probably fooling yourself if you think you can tell the difference between 465nm and 470nm, realistically. Anyways, from what I’ve found, it looks like you’re shooting for light in the 470-475nm range. The LEDs that I purchased were rated between 468 and 475nm, which worked perfect for me.

    The next thing you should think about is your specific tank setup. How tall is your tank? How long? Are there any unique decorations that you’d like to spotlight? LEDs come in many different Viewing Angles; that is, their light is focused or spread out at different angles, from tight focused 15-degree beams, to wide 120-degree angles, and extremes beyond that. I drew out my tank and placed a few different angles to see what I thought would work best for my setup.


    I was just going for best overall coverage, with minimal hotspots. For me, 4 LEDs at 40-degree angles sounded good.

    If you’d like to skip the choices, and get right to buying, see: “Section F: Links” for the LEDs that I bought. I thought they were a nice combination of Viewing Angle, Brightness and Color for my application. As long as you don’t buy at the extremes, (like 15-degree lights) you’ll probably have a hard time telling the difference in the end.

    Also, see “Aftermath Tweak #2” for another recommendation/afterthought on your LED purchase.

    The Resistors:


    These are vital to the operation of almost any LEDs circuit. There are situations you don’t need resistors, but almost anyone will tell you that any good circuit design will incorporate at least one resistor for any given number of LEDs.

    We’ve talked about why you need to use a resistor, and by now, you should know what values you’re going to need to get. Once you find out what Ohm value resistors you’ll need to power your lights up, I’d suggest getting a few extra (they’re dirt cheap, especially online). I ordered something like 15 or 20 of each size the Unique-LEDs had to offer (they were only $0.04/each for 10+ units! Why not get extra?!) If you end up in a situation like I did (see “Aftermath Tweak #2”), you’ll be glad you had a few extra with a few different ratings.

    Once you get a hold of a few resistors, it would be good to learn how to read the values on them. You’ll notice that there are some colored stripes around the resistor, and guess what, those colors tell you the resistor’s ratings. Here’s what each of the colors represents on a standard 4-band resistor:


    To read the value, first you have to have the resistor facing the correct way. Look for a Silver, Gold, or (less commonly) a Red stripe, and place that color on the far right. This stripe tells us the Tolerance of the resistor, and will always be the last stripe (hence, we rotate the resistor so it is on the far right).

    There are 5 and 6 color resistors out there that make reading them slightly more difficult. In addition to the extra color band, with a 5 or 6 color resistor, the Tolerance band is more likely to be a common color, and thus making it a little harder to determine the “starting” band. We won’t dive into these resistors because I feel you’re more likely to run into 4 color types for values needed for this project, as well as if you pick them up locally at an electronics store. You can Google “resistor color codes” to decode 5 color resistors, if you just happen to have some; and there’s a link to a simple 5 or 6-band decoder in Section F: Links.

    Once we’re looking at it the right way, we can read the first three colored stripes to find the value. So if you took a look at the resistor in Fig C-6, you’ll see a yellow stripe, followed by a purple stripe, then a brown stripe, and finally the gold stripe. Read the values and you get 4, 7, 10 and 5%. String the first two together, don’t add, subtract or multiply, but just place them together (4 & 7 = 47); and then multiply by the third (47 x 10 = 470), and you have your value. This one happens to be a 470-Ohm resistor, with a 5% tolerance.

    After a few, you’ll be able to read the values of almost any resistor in only a few seconds. Handy to know if you mix them up on the table while you’re using them. A little tip, once you know the value of a set of resistors (assuming you have more than one), I find it really handy to write the value down on the tape strip that usually connects a handful of resistors together (like you can see in the corner of Fig C-5).

    The Rest Of The Gear:
    Everything else is pretty self explanatory, so we’ll just note them quickly here.

    Wire: Nothing real special about the wire you need. I used a spool of small gauge speaker wire in my setup. Depending on you’re setup, the length required will of course vary. If you were to go out and buy some, I would suggest a small spool of 22 gauge, stranded, 2 conductor wire, with polarity indicators. You can pick up such wire for about $10/100ft. But you can use almost anything here. If you use a single conductor wire, try to use two different colors, one for positive and one for negative (usually red and black, respectively). If you use a 2-conductor wire, the polarity markings (that is, the writing or white stripe on one of the two wires) are very helpful.

    Heat Shrink: I love this stuff. It makes quick, easy and professional looking connections. If you don’t know what it is, I’ll leave this one to you to figure out. You can grab this stuff almost anywhere, from your local home store in the electronics section, a lot of automotive places, of course somewhere like Radio Shack, and definitely online. Highly recommended for the perfectionist, but definitely not required.

    Electrical Tape: Standard black electrical tape. Used in place of heat shrink, and in a few instances where heat shrink won’t work. If you don’t have some, you probably should anyways; even if you don’t use it for this project, it would be good to have around.

    LED Holders: These help give your project a finished and seamless look when you’re done (see Fig D-6). You can get by without these, and mount your lights in any creative way you want, but these make the job pretty easy. If you’re ordering you LEDs online, you should consider a few of these to at least check out. Most places that carry the bare LEDs will also carry holders. If you don’t use them, they’re only a few cents down the drain. Recommended.

    Toggle Switch: Optional, but necessary if you want manual control over your lights (as opposed to unplugging the cord or removing the batteries). I didn’t wire one up on my setup until the second night. My tank is in my bedroom, and I woke up the first night to my wife ripping the cord out of the wall with a handful of aggression, saying that is was too bright and she couldn’t sleep. Needless to say, by the next day, I had a switch wired in (and toned down the brightness a little; “Aftermath Tweak #2”), so that she at least had an easier way to turn them off. Since I was just planning on letting my timer take care of the On/Off, the switch was an afterthought. Consider your own needs on this one.

    Utility Knife: Used to cut things, like wire, or plastic from your hood. The one tool you really can’t do without, unless you have almost EVERYTHING else listed. You’ll see what I mean.

    Multimeter: to check voltages and resistance, not necessary if you are sure of your numbers (mainly source voltage).

    Wire Strippers: Again, nice to have, but the knife can be used here if needed.

    Soldering Iron and Solder: For rock solid connections. Physically joins the wires together to ensure a good connection. Recommended. The old “twist together” method works with two wires, but you’re not really going to be able to “twist” the leads of the LED to the wire. You could twist your wire around the leads and tape it tight, but it’s not a secure connection. Just be aware. If you have a choice, select a low power soldering iron for this job (15 Watts is good). LEDs are sensitive to heat, and a high-powered soldering iron can get hot enough to destroy them. As a general rule, don’t spend more than 1 or 2 full seconds in contact between the iron and the LED’s lead; any more than a couple seconds and the heat will transfer far enough into the head, and get hot enough to do permanent damage.

    Drill: Makes nice holes in your hood. Used for the LED holders, the switch, and the cord from the power adapter out of the back of your hood (if you’re using a wall wart).

    IC Breadboard: Definitely not necessary, but I did use it, so I thought I’d list it. Google it to read more about them, but they’re basically like a lego set for electronics. It’s a board with a bunch of holes that are connected in a specific way, that you can just plug in your pieces (LED, resistors, switches, etc.), and test out your circuit before you solder anything together. It’s nice to have to troubleshoot things, and quickly place and replace resistors to find values that work best for you. I used this mostly for “Aftermath Tweak #2”, but it can be similarly used any step along the way.

    Helping Hands: I remember having one of these things since I was a kid, mostly because I thought it was a cool robot toy. Again, I’ll leave you to Google it if I’m speaking Greek here, but there’s a link to a cheap one that I’ve used in the Links section, and it works fine. Nice to have to help you make steady, clean solder connections (assuming you don’t have superhuman robot hands that hold tiny parts perfectly still).

    Putting it all together… finally!

    Finally, the part everyone’s been waiting for, right? So how to we put this thing together? Well, with as much background info as you have, you should probably already have a pretty good start on how this is going to go together.

    First, open up your hood. If you remove the fluorescent tube, there should be a set of screws that hold the white “reflector” to the black outer shell.

    With those screws removed, the reflector should lift right out. It will still be connected by the power cable running through the black case and into the fluorescent light’s transformer box, but you should still have plenty of slack in the wires to open it up and set the reflector down next to the case.


    This is where I would decide on where you want to run your LED’s. Spacing isn’t critical, but they should probably be pretty close to balanced (unless you are going for an angled light source, or trying to highlight part of your tank). Either way, mark where you want your LEDs to go on the inside of the reflector. Of course, try to place your lights in a spot where you have room to work. Right next to the transformer box might not be ideal. You’ll notice a few yellow check marks on the photo above; this is where I would place my LEDs for the best overall coverage. The choice is all yours though.

    After you know where you want your lights to go, grab your wire. Go ahead and just stretch your wire from your LED placement marks to about the center of the hood (or wherever your going to centralize your cords), and then add about 6” just to be safe. The wire lengths don’t all have to be the same; the wires running to the innermost LEDs can definitely be shorter, and leave the longer ones to stretch to the outside. This will save you a bit of wire too.

    Once you have all your lengths of wire cut and ready to go, we’ll go ahead and attach an LED to the end if each one. You’ll need to strip a small amount of the insulation away from your wire, maybe a 1/4” or so. Connect them however you think best, but I soldered mine together as shown below.


    1. The LED lined up and ready to be soldered together. This is the shorter cathode lead being attached to the clear wire (my wire was clear, and clear w/white stripe. I used the clear w/white stripe as my positive).

    2. The finished soldered joint. It might not be the prettiest solder joint ever, but it definitely gets the job done!

    3. Finished soldering the anode to the positive wire.

    4. Using electrical tape, I isolated one lead by completely wrapping it up. Sorry for the slight blur.

    5. With a decent wrap on the first lead, I just wrapped the tape around the whole thing to cover everything up. Bam! One LED wired up!

    There are a couple things I’d like to point out here. You’ll notice the use of the Helping hands, quite helpful indeed. I used a bit of paper in the clamps as a cushion to help avoid any damage to the wire or LED. And in this particular application, I ran out of heat shrink, so had to go with the tape. Not my first choice, but it worked. Also, you’ll notice the extra plastic piece on the LED (pointed out on the final photo). This is the plastic sleeve that is used to pressure fit the LED inside the LED holders. It’s a simple sleeve with two holes for the leads to slide through. If you’re using holders like mine, be sure this sleeve is on BEFORE you make your connections.

    Before you get all of your LEDs connected to the wires, consider where you want to place your resistor in the circuit. I believe that you can place it anywhere in the circuit, as long as it’s in there somewhere. I like to think of things very linearly, and thought that placing the resistor in the circuit before the first led made the most sense. This is just my preference, so feel free to experiment.

    This is what I did on my setup. I soldered my resistors right to the anode of the first LED. This was for two reasons. First, I’m kind of lazy, and connecting the resistor to the LED lead meant that I wouldn’t have to cut and strip wire anywhere else, the two ends just needed to be trimmed and soldered. And second, this helped me remember which light was my #1 in the circuit (doesn’t really matter, but like I said, linear thinker).


    You’ll notice that in the photo above I’ve covered the whole resistor and connections with a single piece of heat shrink. Again, if you’re using the LED holders, make sure they’re on BEFORE you solder your stuff together. I don’t know how many connections I went back and broke because got in a hurry and forgot this.

    Once you have each of your LED’s wired up to a length of wire, you can go ahead and connect them together. Connect the negative from LED #1 to the positive of #2, then the negative of #2 to the positive of #3, and so forth. In the end, the positive wire coming off of the #1 LED, and the negative wire from the LAST LED should be the only free ends left. I don’t have an actual photo of this step, but the following diagram should explain things well enough.


    The length of wire at “X” is where you decide how long each wire needs to be, depending on your specific situation. If you don’t want to think too much about it, just use a good long piece of wire for each LED, and make them all the same length. It will all be tucked up into the hood and out of sight in the end anyways; but of course it will use more wire.

    This is the overall diagram, and we haven’t connected the power source or optional switch yet, but…

    When all of your lights are connected together, and you’ve got your resistor somewhere in the circuit, this is where I like to test them to make sure everything lights up. I’m skipping ahead a little bit, but here’s where I like to grab my power adapter (or battery pack), quickly twist the positive to the positive, and the negative to the negative, and plug it in. If everything lights up, pat yourself on the back, you’re almost done!

    Note: be cautious if you do this, especially if you're using a power adapter plugged into a wall outlet. If you power up the circuit without insulating all of your connections, you could short something out. Be aware of your positive and negative connections, and don’t let them touch each other. Once you finish your quick test, unplug and disconnect your twisted wires. Better safe, than on fire!

    Once your lights are all strung together, it as easy as popping a few holes in your hood, fitting in the LED holders (optional), and placing your lights in.

    I would suggest here that if you’re not using the LED holders, or something similar, that you make your holes to the width of the LED (5mm in this case), so that the head will stick out, but the shoulder will not let it pass all the way through (the shoulder on a 5mm LED is typically just under 6mm). Then, I would attach the LED with a quick dab of 100% silicone (aquarium safe, of course). The LED holders take care of all of this for you, and is why I think they’re definitely worth the 10 cents.

    Once you have the holes for your lights, if you’re using a power adapter, you’ll need to pop a hole in the rear of the hood for the cable to come out. I like to place this close to the existing cable, just so cable management is easier when it’s on the tank. Also, if you’re using a switch in the circuit, you’ll need to put a hole in somewhere for that. Again, I like to place mine right next to the fluorescent light’s switch, for consistency.

    When you’ve got all of your holes ready, run all of your wires where they need to go, but do it “dry”; that is, don’t tape or solder anything up yet. Make sure that your switch is in the hole, and your wires are all run through the holes they need to be BEFORE any solid connections. I can’t tell you how many time’s I broke solder joints because I forgot to run the wires out of the hood to the switch, or I forgot to put the switch’s screw bezel on before I wired it up.

    Here’s a few last “in-construction” photos, just showing the wires running to the 4 LEDs, the power adapter’s cord running out the back, and the switch right next to that.


    After it’s all wired in, plug it in, and flip the switch if you have it, and see if it still works! There wasn’t too much in the last few steps you could have done to mess it up, but if it doesn’t light up, double check all of your connections, including the power source, and the switch.

    And that’s about it! Tuck everything up nice and neat, try not to bend any of the LEDs leads over, and close your hood up. If you remember, it came apart pretty easily, and should go back just as easily. You’ll most likely have to rearrange the old wires and new wires, but just gently coax everything back into place. Screw it back down and do one final test. If it still lights up, congratulations! You have just finished installing a custom LED moonlight kit!


    Above are the finished shots of my first hood that sits on my 29g tank; the same tank from the photo from the very beginning (the daylight/moonlight transition photo)

    The intro transition photos are untouched originals. They were however, taken after a few tweaks to the system. And that brings me to…

    Of course it’s not done yet!

    Okay, I’ll make this park quick though. There were two things I did AFTER I finished the setup exactly as I’ve laid it out above. These were a couple of simple, quick fixes, but overall were a necessity for me.

    Tweak #1: Diffused LEDs
    This one came about because I noticed that the LEDs had quite a bit of hotspot on the bottom of the tank, directly below each light. They basically act as tiny spotlights, and each shot down into a bright circle, with a little spill between them. The effect was still just fine, but I didn’t like the blue rings I had on my gravel. If you’ve got a less-empty tank, you might not even notice.

    To fix this, I came across a guide on Instructables.com about diffusing an LED. I can’t take credit for this tweak completely, but this was a good idea that I borrowed (the link to this is in Section F).

    If you take some fine sandpaper, and gently buff the LED’s lens, you will give it a more solid, translucent look. I used 400 grit paper, and it worked perfect. I stress the word “gently” here, as too much pressure, or too much sanding can dig into the lens quite a bit and create flat spots. Just work the whole thing over, and once everything is sanded, you should get something like this:


    If you do this, you’ll have to have access to the entire LED, which means that if you got it all put together and closed up (like I did), you’ll have to open it back up again.

    An alternative to this is to just buy diffused LEDs to begin with. I didn’t think about it until I already had the lights in my hand, so this was a very comparable solution for me. If you’re buying your lights AFTER reading this, then you might consider going with a “diffused” one, and you might even get a better result.

    Tweak #2: Dimmer Light:
    This one came about at the hands of my wife. As I mentioned before, she subtly mentioned on the first night that the new lights were a little too bright. This one was a quick easy fix, but required yet another tear-down. The easiest way to dim the overall light output of the LEDs, with what I had on hand was to increase the value of the resistor in the circuit. This is simple logic, if you increase the resistance, you decrease the juice going to the LEDs as well as the level of light that they output.

    In my initial setup, I used a 47-Ohm resistor, the minimum value to get the peak rated brightness. I really didn’t even consider the level of brightness until my wife “pointed” it out to me. Long story short, I opened it back up and swapped the 47-Ohm for a 470-Ohm. This is where the breadboard came in handy. I wired them up through the breadboard and just kept swapping out the resistors until I got the brightness I was looking for.

    If you end up in this situation, I would suggest shooting for the dim side. I find that you might initially think that it’s too dim, but that over time, you’ll grow to appreciate the low light. And also, the level of light will affect your fish. I don’t have any extremely nocturnal fish, but in one of my friends tanks that we installed the lights on, his Ghost Knife will come out to play with the moonlights on, and will only very rarely even show himself in the daylight. Even then though, he says that the Knife will still tend to hang out in the shadows of the moonlights. I think this just goes to show that the light level is enough to make him comfortable, but still a tad too bright to get him swimming out in the open.

    I’ve read a lot of people saying that when they’ve first installed some sort of moonlight, that they were too bright, and that their fish never had a true night cycle, and thus never slept. This is why I’d say to shoot for the dim side. Better to not stress the fish out as you tweak and find the right level of light.

    There's too much info out there, really.

    I’ve got a few helpful links below. The first group is a set of links for the individual parts and pieces you may need to complete this project. These may or may not be the actual parts I used in this guide. These are just links to acceptable parts that you may use as a reference when shopping for your parts.

    The second group of links is a set for additional information, should you need it for your specific situation. This includes technical data, calculators, and articles about LEDs. I would like to think that most of the links in this section are completely optional reading. I hope that I’ve done a somewhat decent job of detailing what you need to know to complete this project, but you can find more into below.

    Unique-LEDs Blue LED - which I used in this guide
    Unique-LEDs Blue LED – diffused, which I think might work better
    Unique-LEDs Resistor Selection
    Unique-LEDs 5mm LED Holders
    RadioShack Resistors (higher priced)
    RadioShack Wire

    Harbor Freight Helping Hands (cheap, but they work!):
    LED Calculator
    4, 5 & 6 Band Resistor Decoder

    Instructables Dimming
    LED Wiring Info 1
    LED Wiring Info 2

    Now it’s done.

    I would like to thank the reader for being patient enough to make it this far. It is my hope that this guide helps just one person achieve such a neat result on their own tank, in their own house, and most importantly, by their own hand. If you just happen to be that one person, please just say “Thanks”. Also, if you could post a picture here in the thread, I’m sure others would also enjoy seeing how it came out.

    Although I’ve tried to verify just about everything I’ve put in this guide, I cannot guarantee that everything is 100% accurate and complete; but hey, I’m human. I’ll kindly admit to any mistakes though, and try to clarify or correct them.

    I’ve tried to cover just about everything you could possibly need to know, but if you have any questions, feel free to post them and I’ll try my best to answer them.

    I would also like to note that I’m going to go ahead and retain all of the rights to the above content, including all of the copy, photos and graphics. This guide may not be reproduced, either in part or in whole, by anyone or any other website. This guide was originally posted on AquariaCentral.com, and should be found nowhere else. This is a lot of info that took me a good chunk of time to compile and format, and I appreciate your understanding.
  2. blissskr

    blissskr "Who's Barry Badrinath"

    Jun 22, 2008
    Likes Received:
    New Hampshire
    Nice well written guide!
  3. chally567

    chally567 AC Members

    Dec 22, 2006
    Likes Received:
    nice guide and how much did it cost you
  4. AcydFlames

    AcydFlames Ideas Guy... Sometimes

    Sep 23, 2008
    Likes Received:
    Thank you.

    I knew that was going to be one of the first questions I got. I almost added a section for cost breakdown, but ditched it at the last moment. But here goes:

    Materials I already had on hand:
    Plenty of wire, tape and heatshrink, plus a perfect power adapter.

    Things I had to buy:
    4 x Blue LEDS @ $0.30 each = $1.20
    1 x 470-Ohm resistor = $0.05
    4 x LED Holders @ $0.10 each = $0.40
    1 x Rocker Switch = $2.99

    Total Cost: $4.64, plus a few cents for tax.

    Not to shabby for $5 bucks, eh?

    Oh, and maybe add another $5 for the timer I used, if you want to count that.
  5. BoredAgain

    BoredAgain Cubs in '10

    Jan 12, 2008
    Likes Received:
    Denver, CO
    Definitely thorough.
  6. AcydFlames

    AcydFlames Ideas Guy... Sometimes

    Sep 23, 2008
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    Yeah, I was shooting for a little overkill :)
  7. beeZer350

    beeZer350 Likes Expensive Hobbies :(

    Jan 19, 2008
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    Wow, excellent DIY instructions.
  8. 1oooop

    1oooop int x; if {x>1} {std::cout

    Jun 5, 2008
    Likes Received:
    here, there, everywhere
    Real Name:
    ns instructions, I did the same thing... just with a 3.3 v and I made it completely waterproof...
  9. Reddog80p

    Reddog80p Permanently Dechlor'd

    Nov 18, 2006
    Likes Received:
    Northern Illinois
    Nice Guide :thumbsup:
  10. AcydFlames

    AcydFlames Ideas Guy... Sometimes

    Sep 23, 2008
    Likes Received:

    I thought about the waterproof thing, but given where I mounted them, and the fact that the entire hood sits on top of a piece of glass (that's sealed), and that the fluorescent isn't waterproof at all, I figured in this case it wasn't necessary.

    But just out of curiosity, what did you do to make it waterproof? I was thinking a dab of silicone around the exposed part of the LED, along with a circle around the LED holder on the inside, and a quick shot to hold the LED in the holder, and it would be pretty much bullet proof

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