My filter has a black "sponge" like thing in it and a cotton like thing witht the charcole stuff in it. The black thing, it's more like a scrubbie in texture is in front of the other thing, the one with the charcole stuff in it is what I change, I've had the tank for 3 months now and have changed that once. The testing thing I have is a bunch of strips you dip into the water and has little square pads on it that change color, I don't know the exact readings just that they turned to the danger color which was bright pink. For the nitrate that makes it 160-200 and for the nitrite 5.0-10.0. Now when I have cleaned the filter parts I have always cleaned them in the sink, so I should be cleaning them in the old tank water? Also about the irridesents, I think I've found a home for them my cousin has a friend whos mom has an outside pond that she has a bunch of those big gold fish and a few other types of fish in and she said once they get big enough she would take them, she wants them to be around a foot long first though b/c she is afraid the other fish would eat them if not. That was one of the things the fish store misinformed my son about they said they would only get to around 6-8 inches found out they can actually get to be 3'!! I contacted the store manager and tried to return the fish and he kept trying to tell me there is no way in an aquarium they would get that big, I told him they may not but it is not healthy and I didn't want to keep fish I knew in the long run I would harm but it was all for nothing.