500 Watts of Metal Halide!

[CrohnieBoy]

All:

I am thinking about using two 250 watt MH bulbs to light my 125 gallon tank.

some plants, schooling fish, NO co2

Is this too many wpg?

Comments?
Suggestions?

I have a feeling Barr and others are going to tell me I will have more algae than fish, but want to hear the collective's opinions...

:)

[cdawson]

No way!!! Drools..... I've seen a planted 90g w/ co2 (BTW you better use CO2) and two metal hallides bulbs....it was awesome.
I actually think you should be using CO2 for that many WPG.
It also depends on the type of plants you want. Make sure you use background plants for the background, mid range plants for the middle area and so forth. You actually only have just under 4 watts per gallon with those lights and some people use 5. Just control the nutrients everyday and you're not going to have too much algae.


BTW this should've been posted in the planted forum.

[CrohnieBoy]

lol; thanks for the drool,... i think ;)

So how do we go about getting this moved?

I couldn't decide if this post was best in here or the planted section, so you are the tie breaker.

(Looking up to the skies): can someone move this?!? ;)

[Cearbhaill]

I'd be looking at the heat they generate.
I'm in such a hot climate that to challenge my A/C that severely would be silly. I can't get my living room tank under 85ºF to save my life as it is.
But if you're in a cooler climate and need the heat that's a different story.

[HungryGoldfish]

You'll also get the cops knocking on your door asking where the pot is.










(some reef people consume so much electricity their power bills go through the roof and the police suspect indoor pot growing. Other times they use heat-imaging to determine unusual areas of heat, also suspecting indoor lighting for pot plants).

[Fishiebusiness]

You'll have to be careful with that much light, your plants will be at a high growth rate and susceptible to shortages of nutrients which algae will exploit to grow. I think 2x150 watt would be plenty for your situation.

[cdawson]

Yeah I agree, unless you know your stuff stick to the lower wattage. I had enough trouble evening all my nutrients to daily doses in my 50g. I imagine with that much light it'd be expensive to maintain a tank like that every year.

[slipknottin]

Where are the cross bars on your tank? Usually MH bulbs are used to cover a 2' spread.

[Richer]

500 watts of MH lighting for a 125 is far more than you'll ever ever need. Even for a CO2 supplemented tank.

If you don't want CO2, I'm not even sure I would suggest going with MH lighting... far too bright imo. You could probably get away with hanging shop lights from your ceiling, and that should get enough light into your tank to grow plants.

If you want to go the CO2 route, I'd personally go for the 2x150 watt route. That should be quite sufficient for growing a high tech, CO2 supplemented tank.

HTH
-Richer

[The Gipper]

I wanted MH lighting for 10 years, ever since I saw a great 135 gal display tank at the LFS, with 3 x 250w MH pendents and every Dupla product you could imagine. Loved the ripple effect. I've done fluorescent for years.

I have two 175w rectangular pendants on my 120 gal and love it. your 500 w on your 125 is 4 watts/gallon, on the higher side but definitely not excessive.

If your tank is a 6 footer, I agree with Slipnottin about the 2 foot spread. With only 2 lights, you will definitely have brighter and less bright spots in your tank.

I also agree with Richer, in terms of the CO2, etc.
That much light will be EXTREMELY difficult to keep algae at bay without going high tech on everything else (CO2, K, P, NO3, etc)

Read this thread:

http://www.aquariacentral.com/forums/showthread.php?threadid=16177

[cpr4cpu]

i opted for 3x175 MH pendants for my 125. It is an open top tank and the pendants are 18 inches above the tank (so I can do maintenance and the heat won't burn ther plants)

The more space from bulb to substrate opens the cone of light so you have more "optimum" mid and high light range.

Lastly, a good rule of thimb is 2.5 watts or more per gallon should ideally use CO2 or carbon supplement (Flourish Excel)

[DIYMatt]

The spread of a MH light depends on a lot of factors. Most wether the bulb is mount vertically or horizontally, and the style of the reflector. If you look at a MH bulb burning you will see that most of the light emits from the sides of the bulb. So when you vertically mount a MH bulb, most of the light projecting downward is reflected light off the reflector. The most effective way to mount a Mh bulb is horizontally perpendicular to the the back of the tank with a good reflector. That way you have a rectangular light pattern. So then, I would say that a 150-175W metal halide bulb mounted horizontally will effectively light to high light level a 4' sq. ft area, but one that is more rectangular. The traditonal pendants throw light in a circle that I would also say is about 4 sq ft in area, but will be slightly less intense. To me two 250W Mh's horizontally mounted in an effective reflector would be excellent for a 125g tank. I run two 175's on a 75g tank. All that being said, It may come down to aesthetics. Three small "pendant style lights would look FANTASTIC over that tank and light it well. Two horizontally mounted MH's would be big bulky fixtures and I haven't seen many that look all that great. But it would be great lighting. Just like everything else in this hobby, there is no right answer, only options.

[Robert H]

A MH bulb emitts light in a triangle pattern with the brightest light being directly below the light. Each bulb covers about a 4ft square area. This is when hanging above a tank. I have never heard of having a bulb mounted horizontal, and do not quite understand what he is reffering to, but plants have to have overhead lighting.

Its not too much light for a tank that size...if you have C02. It would be foolish to run it without C02. If you want to strive for algae free...you have to have balance of light, C02, and macro and minor nutrients. Anything that becomes the limiting growth factor for the plants will start an algae bloom, and not having C02 with that much light would definetly be a limiting factor.

Heat may not be a big problem if you are going to be using suspended spot lights on an open tank. If you are talking about MH lights in a closed hood system, then heat will be a big factor. Open top tanks can look awesome.

GADZOOKS! Two 175 watt MHs on a 75 gallon freshwater tank?! One would be plenty!

[newreefers]

I happen to have a 125 saltwater tank and run 3 250w MH lights.

My system is not an open top. It takes 6 fans running while the lights are on to keep the temp down to 82 degrees. This in a house where the thermostat is set at 75 degrees 24/7. Without the fans the temp gets up over 90 degrees.

Also, yes the bulbs are horizontal not vertical. Most MH lights mount this way if they are not the pendant type.

[DIYMatt]

Robert - Actually, I don't think it is too much light, IME(which is admittedly is much less than yours). I have found that it is the only I have been able to get plants like glosso to grow horizontally. Also, on both of my MH(both over 4wpg) lit tanks, I have had very good luck with them. IN fact my 75 does not have CO2 supplementation. I have just found I have to be on top of the nutrient levels, and there are certain plants you just can't grow successfully without CO2. For example I do not dose NO3, but I dose very small amounts of PO4, very little supplemental Fe, but pretty heavy amounts of Flourish. Actually, I had a 55g with 110w CF and and I battled more with algae and there were a lot of plants I couldn't get to grow well. But, this is just my experience that admittedly doesn't always jive with others. I don't know if it has to do with my 4000k $20 halide bulbs or what. But, high lighting has always worked very well for me.

All that being said, I think two 250w Metal Halide is probably more than you would need over a 125 gallon without CO2. CO2 supplementation would definitely increase your chances of having the beautiful tank you want.

The shape/style of the reflector will be a huge factor on the coverage of a Halide bulb. IMO - it is a little too general to just say a MH lamp covers 2 feet of tank or 4 square feet. That may apply to a pendant light. But, a high wattage MH bulb in a horizontal reflector ABOVE THE TANK can cover a much larger area, especially if you hang it higher above the tank. As far as I know, the intensity of the light from a MH light doesn't drop as fast a flourescent the farther you get from the bulb. Just my two cents!

Robert - I meant a horizontally mounted BULB in a reflector. But, it is still mounted above the tank. I'm surprised you don't know about this, IME most of the MH's are horizontally mounted in hoods. I also agree with you, MH in a closed hood is probably not a good idea due to heat, especially if you have the ballast in there too. I would stick to open tops with MH, yes they do look awesome.