I have a little sponge filter that isn't hooked up hidden behind some rocks in my 110 gallon show tank. The sponge was used to seed the tank so it was filled with beneficial bacteria. I've been keeping it in this tank thinking that if I need to set up a hospital tank, I can just set it up in my 15 gallon. Is there any problem with having it sitting in the tank without having it running? Is it a reasonable assumption to think that it will still have beneficial bacteria?