Have enjoyed this forum for quite a while but this is my first posting. I have a 10 gal tank that I would like to use for a quarantine tank. I have an established filter to put on it and was going to put 5 gals of water from the main tank and 5 gals of new water in it and leave it bare bottom. My question is how do I keep the biological filter going if there is no fish in it so that if I purchase a fish it will still be ready? Thanks in advance.