I don't think a lizard tank would be a good growing vessel. If you go with a natural soil mix you have no way for it to drain and water will accumilate at the bottom (not good). If you go hydro then you'll need to lightproof the entire tank and also get a lightproof lid.

I'd skip the tank and maybe buy a 5 gallon bucket with lid at Home Depot. With this you'll have alot more options.