I had salt water tanks for years, I don't know alot about fresh water but if they are all hand size a 36 gal may not be large enough . I also agree that three times a day is probably way too much depending on how much you are feeding of the food if it is only a flake per fish it may be a diffrent story . I know many of my salt water fish only required one flake per fish per day . I am glad you rescued them though, Fish are very relaxing to watch I miss my fish they each had their own personality
