Funfin... I have a canister rated at 2000lph, 4 internals that are about 250lph plus a hob rated at 600lph. In my canister I have Matrix, plastic drinking straws, bits of sponge and bioballs, though I intend to remove the bioballs for more matrix eventually, the internals hve sponge, Purigen and Matrix and the HOB has sponge.

I put the stones in there to allow them to use their natural behaviours but not so much that it creates a problem with waste, and the java moss is so soft that they love playing in it and nibbling any food that falls on it.

I once had a tank wih gravel and stony substrate....NEVER again, it was a nightmare, my hat is off to those who do it but it is definately not something I can maintain. I hope one day to have an indoor pond probably in the next couple of years, certainly when or if they get to those huge sizes, should be a blast to do!