Which External Filter Media

[crackmonkey]

Whats the best thing to put in an external filter for freshwater puffers, I have two media trays. In the bottom is gravel & biomax, middle is filter floss and top there is nothing.

 

[CFC]

I fill my canisters with ceramic rings for the first stage, eheim efi substrat pro for the second, eheim efi mech for the third and then sponges to take up any room that is left. This combination gives the maximum biological capacity possible without changing to sump filtration which is important when keeping fish with predatory dietry requirements.