gravel?

[zigog]

do i need gravel at the bottom of my tank?

[colbyrs]

It's best to have some sort of drainage at the bottom of your tank. You don't "need" gravel. You can use egg crate, clay balls, or gravel. But beware, gravel is very heavy and packs together. The clay balls are light and take up more room with less weight and they don't pack together. Some people just use one of these options and others use two or all three with the use of screen to keep substrate from falling through. Check out some construction journls on here and you'll see how important it is to use some form of drainage.

[zigog]

can i use crushed clay pots?

[Rainfrog]

you want something that can let water drain from your soil. you will want to put some kind of screen or mesh between the drainage and the soil to prevent the soil from packing into the drainage material and clogging it up.