good job on trying to improve your fish's quality of life. i'd personally suggest that you add at least a 20, better yet a 40 watt grow light(eco lux are like 10 bucks everywhere) and two more cuttings to each planter and one of those hermit coconut climbing walls so the pothos have something to climb up(not essential but makes a better presentation). with the light the pothos's growth will take off using up all that nitrogen and what not. My opinion is fancy goldfish have extreme physical deformities and placing them in large tanks with overpowered filters may force them to work more then their bodies may be able to handle. esp. not knowing the lineage of that fish. With that said i keep my fancies in those 8 dollar round tubs they sell for storage/ice buckets at most department stores. they hold about 18 gallons of water and make really nice indoor ponds esp with the 40 watt lighting suggested. But these are just my opinions. seems like a return to the store is never the best solution.