So, we bought a used tank and stand. It came with a canister filter. It was full of media and was still full of water. The seller removed his fish Friday night and we picked up everything Saturday afternoon. I couldn’t get our new canister up and running until late Saturday night. I used the biomedia from the old canister in our new canister. I don’t think any B.B. survived. It was in stagnant water for over 24 hours, so I guess without flowing water and oxygen, I think they’ve died. My main worry is that when we went to see the tank, he had a few fish in there. I think they were all near the end of their lives, he said he had had them for about 10 years. One Jack Dempsey was swimming really funny at the bottom of the tank. He looked like he was dying. The seller (seemed like a very nice, honest guy) said that the fish had been that way for a long time. But he keeps eating and trying to keep up with his friend, another Jack Dempsey. So maybe it was just old age and his body slowly shutting down. This is my worry, what if these fish were diseased? And I’ve thrown the biomedia from that tank into my brand new canister filter. Have I contaminated my new set up and will it make any new fish sick? We are fishless cycling right now, so it will be a fair few weeks before I have to worry about adding fish. Is there a problem with what I did? And how do I remedy it so as to not introduce illness to my new fish?