Please NEVER return these fish to the wild, especially if you add any other fish from different areas of the world (or LR, etc). You can introduce foreign parasites or pathogens back into the wild.
You are, IMO, obligated to kill them should they outgrow the tank...and I suspect they will.
There are better ways -- I am sure you will hear :lol: -- to cycle rather than using live fish, IMO. But my greater concern now is that you do not ever release them back to the wild.