min tank size for a flame is 30 I read so he should be good.
Do not do garlic soak daily, to much garlic is worse than none. It can compromise the fishes immune system, cause internal damage to the digestive system, and diminish water quality. A little goes a long way.
Edit: keep in mind that the fish that are to large will remain stressed and will be at risk for a breakout again in the future. After they look better you might want to consider an upgrade or rehousing some of the "larger" fish. This will benefit your wallet, your tank, your piece of mind, and the fish.

