I would remove the pleco. Lupe is (as always) completely correct about 29 gallons being sufficient for a fancy goldfish. Goldfish, are, however, social creatures and tend to fare much better with another of their kind. If you rehome the pleco and get another fancy goldfish, with adequate filtration, the 29 should hold you for a while, and be a very attractive tank to boot, especially if you add a little live vegetation for them to snack on.