My ten gallon guppy fry tank also doubles as a grow out tank for my plant prunings. I have a 2 inch bed of ordinary sand over a 1 inch layer of mixed sand and laterite. The cheap-o hood that came with it normally houses a pair of incandescent lights. I replaced those with two screw-in 10 Watt
CF lights (about 5 bucks each at good-ol Walmart). With that small and shallow of a tank, those lights really brighten up the tank. Im not sure that the
WPG rule is quiet the same with smaller tanks. My plants grow quite well in this setup and the only issue Ive had is having to clean the algae off the glass from time to time with a mag-float. I've contemplated adding a small
DIY CO2 setup in order to help control the algae. I do perform regular water changes and also dose fertilizer in small increments, but the plants seem to grow equally well without the ferts. There are about 30 Guppy fry in the tank and my Nitrate levels stay pretty constant around 20
PPM. As of now, about the only plants I have in that tank are a lot of Anachris(which grows in the toilet), Rotala Indica, Ludwidgia Repens, Cabomba and a small Radican Sword, which is looking quite nice.