Yeah I've got a breeding pair of golds in a 55. They get pretty decent sized, and are pretty fish. I keep the temp around 78-82 and filter it with 2 xp2s, which is probably overkill but it works. I don't use any type of airstone, I have the spray bars from the canister just under the surface of the water. They eat mostly flakes and pellets, occasionally feeder guppies. They lay eggs every 3-4 weeks but I have yet to have any fry survive.