I have a 120 gal tank with an undergravel filter and a couple of Aqua Clear bio filters that hang off the tank. My fish are mostly cichlid and some cats. I want to switch out the undergravel filter for a cansiter. What is the best method for doing this? Should I retain some of the water and hold my fish in a large bucket while I pull out the undergravel? I'd like to thoroughly vacuum the gravel once the filter is out and I don't want to harm my fish. Also, I've read on different sites that you don't want to change out more than 50% of the water. Is this accurate?
Some advice would be greatly appreciated.
Some advice would be greatly appreciated.