I have gathered everything to set up my frog terrarium the tank or cage is a exo-terra small tall 18X18X24 I have a question I see on some sites they use a false bottom like an undergravel filter in an aquarium and some use large rock or other stuff to act as a bio filter. Which is better or is it just preference. If I go the subsurface I have a bunch of Plastic Bio Balls from one of my early saltwater aquariums set up never used. also I have some egg crate to make a false bottom with. What would you recommend thanks for the help