04-26-2008, 02:56 AM
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By too hot< I meant that you had too much light. Kelvins( the "K") is defined as he basic unit of luminous intensity equal to 1/60 of the luminous intensity per square centimeter of a black body radiating at the temperature of 2,046 degrees Kelvin.
Now that I've thoroughly confused you, it is a means to measure light by using the starting point of absolute zero, a theoretical point at which all energy ceases and is no longer emitted. Some have said that it si based on the temperature of the sun as being a maximum. I do not find that to be true. Plants do best at Kelvin ratings beginning around 6700K or just slightly lower and progressing to around 12000K or so. There are some plants that enjoy light around 15000K-18000K but those are few.
Depending on the species of plant you intend to keep, I feel confident that a bulb in the 6700K to 8500K would be sufficient, unless your tank is over 30" deep(top to bottom). Multiple bulbs may be needed to provided sufficient footcandles to the bottom of the tank. I have found it necessary, at times, to use more than a single bulb. In my plant tanks in my fishroom, I am currently using (2)4' 8400K bulbs at no more than 26" above the substrate of any one tank. This puts the plants that I have in the medium light range. Not to say that I don't have low light plants in those tanks, because I do. All lights are on timers interphased to CO2 injection. All kind of trick, but these plants are for profit. Not all tanks are using CO2, but a few are.