Thanks. I'm using a aqua pro external filter but upon opening up the canister there are only empty baskets with the top basket having a medium foam membrane. I've now ordered two kilos of Biohome media and some starter balls to go at the very base. what I'm worried about is eradicating my bacteria from the canister by discarding this membrane. Suggestions on this would be appropriate if you have any. I did change the carbon filter in the system and my protein skimmer seems to be working fine. I have also carried out a water change of about 10 percent baring in mind that's the third in a week do to the way the tank came.I tested the NO2 last night and it had dropped a little but i will keep monitoring.