02-23-2009, 09:22 PM
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Watt per gallons. Help!
So I have finished my research on lighting. (thanks Aquarium Lighting; Kelvin, Nanometers, PAR, Bulb, Watt, MH, LED, light basics. )
Where has everyone gotten their basis for watts per gallon? I have read or been told I want about 3-11 watts per gallon. But a watt is a measurement of electricity usage per second. So then I started looking into it, and found that the light produced from different sources provides more or less per watt. This makes sense because back when t12s were the main lighting source for reef aquariums is when the wpg "rule" was coined.
Since the wpg rule was made based on t12s, the coral light requirements more than likely are still rated by watts per gallon of t12s. A t12 at 20 watts will produce about 800 lumen that is 40 lumen per watt. A t2 bulb rated for 13 watts however produces 950 lumen. That is 73 lumen per watt. A MH bulb produces 90 lumen per watt. So saying that one would need 7 watts per gallon can mean 280 lumen per gallon (on t12s) or as much as 630 lumen (MH). With a 100% margin of error this rule is worthless to say the least.
If this werent enough to make me concerned with overkilling my tank on lighting there was an even larger issue pointed out by three of the websites I looked at. That was the PAR and PUR of various light sources. I have no degree but from what I understand the PAR is the is the spectral range of solar light from 400 to 700 nanometers that is needed by plants for photosynthesis. Metal halides produce large ammounts of UV light. Uv light far outside the PAR range it not only is not useful to plants and corals but can be harmful.
Another issue brought up on my main information source (see link at post start) is the optimal tempature ranges to go with. "in better funded tests outside the aquarium industry show that many stony corals, clams, and other sessile species that depend on photosynthesis of zooanthellic algae not only thrive but also propagate with light that achieves the optimum PAR, which is generally found around 6400K, not the higher Kelvin ratings so often put forth (Higher Kelvin outputs are required for tanks deeper than 24-30 inches to achieve maximum PAR, although high intensity 6400 SHO lamps can generally penetrate deep tanks well)."
So based on this information I would like to hear people's opinion on my porposed lighting setup for my 40 gallon. 4 x 96 watt 4 pin square base t5 HO (about 65 lumen per watt) this is about 624 lumen per gallon and is equal to one 277 watt MH bulb. I will have moonlights and will program it it mimic the actual moon's cycle, but that should no matter much.
Just something neat that illistrates my point. My 384 watts (9.1 watts per gallon [1:42] ) will provide as much light as a 277 watt MH bulb ( 6.9 watts per gallon [1:46] ).
Last edited by cal1112333; 02-23-2009 at 09:27 PM..