Your choice and you can do both if you'd like.
Best for me was to leave my tank alone! This was in regard to a bacteria bloom of pretty pearly soup in my tank, and to stop changing the filter pads. (although the guy didn't mention not using tap water to clean them) I was really freaked out about what was going on and several probably 4 different stores employees didn't know either.
Worst was that the fish just grow to the size of the tank and that goldfish don't get that big...(oh and can live in a bowl)