I am a newbie to keeping chams, but I think a planted substrate bottom is a very cool idea:D. I wouldn't worry about the cham poo (fertilizer), but I would worry about getting enough light to the plants in the bottom of a cham cage, without cooking the cham. Too little light, and the ground...
Bradley is correct about UVB lighting outputs. The "5" and "10" on UVB light packaging refers to the ratio of UVB to UVA + visible light. 5% HO (High-Output) tubes (made by some manufacturers) emit more UVB overall than low output 10% tubes, though the ratio to UVA + visible will be lower. Wear...