first, i recommend you get wider pvc pipe than you would think you need for your support struts under the egg crate. so that gives us now the egg crate false bottom. is this tank going to have a water feature? how far from the false bottom is the water going to be? the reason i ask is the "wicking factor". if your water level is too close to the egg crate, it will wick up moisture from below and you will have a bog, instead of a well drained tank. a few ways to combat that are to keep the water level at least an inch below the egg crate, or add hydroton (clay pellets) as a drainage layer on top of the egg crate before adding soil. a lot of people will tell you that that is not necessary, but if you are keeping a close tolerance with water levels, then i think it is necessary to avoid having soggy substrate. remember, soggy substrates grow nasty bacteria, which could affect the health of the frogs. RETF's are sensitive enough without adding another complication.
as far as substrate materials goes, you have a whole lot of options there. your best bet is start building the false bottom. take one step at a time. don't rush anything. keep in mind, this is not an instant gratification hobby. i like to call building vivs "the long con".![]()