I used to use fine silica sand, available from the Swimmimg pool shop. Give it a good rinse. If you wish to breed, then invest in a breeding mop, as they will lay eggs on this and then you can remove this mop inot a fry saver. I would use 3ft tanks , but that is just my view. In the filter intake, put foam over it so the little ones do not get sucked into the filter.
What type are you looking at getting and breeding ?
cheers jk :thumbup: