Since having my first experience with sick fish, I have decided to keep my 20g going for quarantining new fish and sick fish. What should I have as far as equipment? What should water conditions be set to? Thanks for the help.
You can keep it simple. No substrate. You must be sure that the tank does not become reflective at the bottom which does happen when you have no substrate. This is easily avoided by painting the bottom black [on the outside]. Use fake decor or PVC to create comfort zones for your fish. You can choose whatever filtration you want.