I found out that fish flakes alone are not good for goldfish, however I don't know what else to feed him. I have already given him some cooked broccoli, but he didn't seem to like it that much. What else can I use? I have also heard you can give them orange slices and grapes. Is this true? Also, will certain foods cloud my tank's water? I have a filter, but I don't know what will happen.