if you had the above set up ^^^^ i would personally go with some shrimp like amano to keep things clean, get 6 or so and they wont breed as they need salt water soloution. u will need a CUC imo
yes i agree some amanos would be better. even cherries they would breed but there more or less zero on your bio load there recyclers. they eat waste and poo out less
They Are Fancy goldfish..very slow moving veiltails, i have had an all natural tank..where i had kept stickle back in it ..and that seemed to go quite well..