Can you have too many watts per gallon?

Discussion on aquatic lighting.

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GermanShepherdGirl
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Can you have too many watts per gallon?

Post by GermanShepherdGirl »

A friend of mine recently got a 29 gallon. He is going to use metal halide lighting and maybe a florescent. He wants to know if 10 watts per gallon is too much light? I told him I wasn't sure. What do you think?
-Kristyn
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Scott
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Post by Scott »

There really isn't but you wouldn't want to put a 400 watt on a 29. I think heat is more of a concern. At one time I had 1240 watts on my 100 gallon tank and the only problem that I had was heat.
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Fishfood
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Post by Fishfood »

Heat and coral are two of the main things I'd worry about. How much light is too much for the coral you want to keep and can you keep the water cool.
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GermanShepherdGirl
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Post by GermanShepherdGirl »

Yeah I told him I'd be worried about the heat.
-Kristyn
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Post by mykpoz »

also worried about bleaching... just make sure he has some shaded areas, or stays away from the lower light species.
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Post by NM354 »

Heat could be controlled pretty easily i would mostly be worried about corals bleaching out. If you can get the light higher than normal above the tank would help. My friend has a 250WMH over a 30L and it seems to be hard to find places for some coral due to the rediculous amount of light. I would suggest VHO that way you don't really have to worry about bleaching neer as much and the heat will be much less.
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Post by Scott »

If the corals are acclimated to the light properly they shouldn't bleach unless they are low light corals. I had several different species only inches below the suface right under a 400w 6.5k Iwasaki and never had a coral bleach from too much light and at the time you couldn't get any more intense or have any more par than that without going to 1000w.

I keep mostly SPS so my experiences are mainly with them but I have had a green Sinularia on the sandbed under those lights and it grew like mad.
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medikall
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Post by medikall »

Yea, heat causes more bleaching than light from what I have seen. They normally go hand in hand so it can be hard to seperate. One thing to think about, even if you can keep it cool, can you keep the temp stable. If it stays cool with lights on, will the temp drop to fast at night?
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Post by Amphiprion »

I wouldn't personally recommend putting very high intensity lights on a smaller tank. It is certainly true with practically all corals (even typically low light ones) can and will do very well under very high intensities, but in smaller tanks there are several pitfalls. The first, heat, is certainly a problem. If the tank's temp rises above ~84 degrees, then you will have to find something to compensate for this. Lastly is the light acclimation process. In such a small and relatively shallow tank, you are going to have great difficulty acclimating many corals safely (whereas in larger tanks, you place them on the bottom). You will even notice extensive "burning" and bleaching when using the screen method in such shallow tanks (unless you placed many layers on top). My advice, if you do go this route, would be to put it on a cable/pulley system to raise the lights' distance from the water to acclimate them. This would also imply an open topped tank, which would help with some heat dissipation.
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Scott
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Post by Scott »

Amphiprion wrote:I wouldn't personally recommend putting very high intensity lights on a smaller tank.
I kind of agree. It you have a shallow tank (15 inches tall or less) I would go with a 150w (the 50k Iwasaki was getting great reviews last time I looked at them) or even a 70w. If you have a moderately tall tank (16 t 24 inches) like a 15 tall or a 29 gallon I would go with a 175w on the 15 and a 175w or 250w on the 29. My take on this is from a SPS perspective. If you want a softy or LPS tank you could just use a 70w or 150w on anything.

Heat may ne a problem with any tank. Though I have a hard time believing it I have read several times that 400 watt of light will produce the same amount of heat regardless of the type of bulb(s) being used. Oddly enough I alse read that the 1000w bulbs have the same surface temp as a 400w. It has been several years since I read those articals but they seem to contradict each other.

So, the real question is what does your friend want to keep in his 29 gallon reef?
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GermanShepherdGirl
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Post by GermanShepherdGirl »

Thanks for all the tips! I think he only wants to keep the SPS corals. I'll let him know what yall said.
-Kristyn
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