Highest light limit?

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valleyvampiress

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Feb 28, 2005
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I was just wondering, at what point is there too much light? I know 4wpg is quite common for difficult plants, but what about beyond that? The real reason I'm asking is because I have a 20g L with 65watts CF, and a 2.5g with 11watts CF.

The 2.5 is doing good with absolutely no intervention on my part. I don't add ferts or CO2. I have 3 shrimp in there that as a byproduct (not purposely) add nutrients to the substrate. I don't gravel vacuum the substrate (the plants grow almost everywhere). I have some semi difficult plants in there; petite nana, glosso, dwarf hairgrass. They grow slowly, but very green. There is some green algae, but not much. Water changes every week with 75% water change.

My 20g on the other hand, isn't doing well. I add ferts once a week, there's no co2 except flourish excel, i have a small bioload with one ram, and I gravel vac the substrate as much as I can get (some plants are in the way). My plants grow, but not as vibrant as those in my smaller tank.

Here's my question, I know the amount of growth has to do with how much and what kinds of ferts I'm adding. But my plants in my 2.5 are doing great with practically no work on my part. I want my 20g to be as painless as my 2.5. This is the real reason I want to add more light. I would still add ferts, but I want the light to do most of the work. I understand algae will be a problem, but I am willing to deal with it as long as it's just green algae.

So what is the most you can put in a tank? I wanted to do 4.4 or 4.5 like my 2.5g, but for convenience purposes, I want to just get another 24" coralife fixture with a 55watt bulb. That would be 5.5wpg.
 
Jeez! As it is, you already have 3.25 wpg. Why would you want to put more light on your tank? You're asking for trouble.

If you don't have much experience with a medium setup, get ready for some major work. You won't just have green algae, you'll have all types if you don't know what you're doing.

It's no wonder your plants are suffering in your 20g. You're not adding Co2, and your probably starving your plants to some extent. 3.25 wpg is nothing to sneeze at. You're already at a high light level.

Can you give us more details about your tank? Water parameters?

Lissette
 
I understand that balance is the key. At 20g though, CO2 isn't a big concern for me at the moment. I use flourish excel and though the wpg in my tank right now is at a point where co2 would give it a big boost, I'd rather not deal with the whole setup right now. I do plan to add it later, but it's not at the four front. The thing I don't understand is why my 2.5 is doing so great without co2 and ferts. I am drawn to the all natural state of the dutch style tank. This is more what I'm talking about when I mention my 20g. Currently, my 2.5 is surviving off of that type of setup. To be honest, I didn't intend for the plants to survive in the 2.5 (that's why I didn't add ferts or co2), but since they did and grew healthy, I want to mimick that setup in my bigger tank.

The plants in my 20g aren't suffering (well, they are right now cause my light burnt out). They're growing. They're green (or red). It's just, they don't seem as vibrant as those in my 2.5g and I don't do any work in there.

I really just want to know what is the max. I would assume 4.5wpg.
 
might be from the fact that you do gravel vac your tank. if done to deep you could be sucking up all the nutrients from those poor plants. when i vac mine, all i do is agitate the water w/ my hand or the siphon then vac about 1-2" away from the gravel.

much like corals, plants engage in chemical warfare to prevent others from growing in thier space. eucalyptus and brocolli for example secrete poisons that will kill most plants. the fact the these plants are in the water and kept in a small contained environment, facilitates the movement of their toxins. Sometimes plants can survive but are stunted, and combinations of toxins have a compounded effect. In my 55 watersprite either dies or grows extremely slow, in my 10gal nursery watersprite grows so fast ive got to remove it wkly. my guess is that it has something to do w/ the several sp. of plants in my large tank vs the 3 sp in my small one
 
I still think that you need Co2 in your 20 gal.

I had a 20 gallon long with 3.5 wpg. Before I added Co2, my plants weren't looking so hot. As soon as Co2 was added, my plants looked healthier and grew like crazy. Also, adding the proper nutrients balanced it out.

Of course, that was my setup. Everyone's tank is different.

Lissette

P.S.: From what I understand, the wpg rule only applies to tanks that are larger than 20 gallons.
 
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High light, high bio-available carbon, and high fert addition are involved in the rate of growth. A lower light tank, with less carbon/ferts, can look just as good. But it does not grow nearly as fast.
 
do yourself a favor and get a cheap CO2 reactor. I have the nutrafin model (around $20 or so) and it works great in my 29 gallon. in such a small tank like you have, you'd be crazy to get a big $200 setup when such an easy and affordable option is available to you!




Nutrafin CO2 reactor

I'm pretty sure that you only need to order the top item, the 'system' for $23. That ships with the diffuser and some packets of yeast.

Good luck. You'll be happy with the results of the CO2. I know I was suprised, despite all the raving I had read about it. Oh, and that is a pretty **** reliable online retailer too.
 
That's very interesting about the poison. I never even heard of that before.

So is co2 easy to set up and monitor? The biggest thing I'm worried about is constant fluctuations in PH. I'm really fond of my ram and I'd hate to lose him. I actually already bought some of the parts I need for a real co2 setup. I need a tank and a place to fill it up though. That's what's making me lag in getting it. That, and my fear of the co2 building up too much pressure or something.
 
IMO, adding light to your 20 is just going to compound your problem. The watts/gallon rule falls apart when used on a 2.5 gallon tank. The way I understand it, a certain minimum energy input (light level) is needed to grow plants. Your 2.5 gallon is reacting as a moderate to slow growth tank, despite the high watts per gallon. This allows the tank to do well with small efforts on your part. Your 20 gallon has a light level which would be considered high growth. I don't believe CO2 supplementation is adequate and that is why you are seeing unsatisfactory results.
 
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