Originally Posted by aquabillpers
I was using "Kelvin" in the context of growing plants, where the term is essentially synonymous with "color temperature". In the past, a Kelvin of 5000 to 6500 degrees was considered best for most aquatic plants. The sun at the equator approximates that. Are we saying that doesn't matter with LED's?
To restate my question about light and tank depth, how does one determine how many LED's a tank a tank needs?
It would seen that a deep tank would need more light that a shallower one. Some fixtures contain more LED's than others with the same dimensions and they'd then seem to produce more light at the bottom of the tank, but do they?
Fluorescent bulbs have long been categorized as "daylight", "warm", "cool", etc. and more recently by a color temperature, one of which is 6000-6500K. But, even those bulbs didn't really come close to matching a black body at that temperature, because fluorescent bulbs have several high peaks in their spectrum, instead of a continuous, smooth spectrum. Plants don't need any specific color temperature bulb. They do need significant light in several parts of the light spectrum, whatever type of light source it is.
There is no specific equation that I'm aware of for determining how many of what type LEDs are needed for various sizes of tanks. When I was building my own LED lights I measured the light output of single LEDs, and, for tape mounted LEDs, the light output for various rows of tapes of specific types. And, I was able to use that to get a pretty accurate guess about what any group of LEDs would produce.