· Premium Member
I disagree. "High light" is the light intensity that lets you grow almost all of the typical aquatic plants, with possibly some problems with ground cover plants. "Low light" lets you grow anubias, mosses, cryptps, ferns, etc., but will not let you grow plants that demand lots of light. And, only Marsilea is likely to survive as carpet type plant.If you have 56 watts over a 29G tank, that would be low light (1.93wpg). That is enough to grow low light plants, like: Anubias, mosses, crypts, horwort etc..
A 2 x 36 is 72 watts which would give you 2.48 wpg. This would be considered low-medium light setup. In this case you could grow a little more variety of plants.
For a typical shape tank, using PC lights with reflectors similar to AH Supply reflectors, 2 watts per gallon is borderline "high light", 1.3 or so is borderline "low light". Both cases are for lights that are around 2 inches above the water. Raise the lights and the numbers change drastically.
If the 56 watts are PC bulbs with good reflectors, you can grow most plants, so that is borderline "high light", not low-medium light. If the 56 watts are ordinary shop lights, with their white painted housing serving as a reflector, it is low light.
This is, of course, just my opinion and is subject to change as I learn more.