Thanks,Are you using API Test (Notorious kit for measuring ammonia wrong and high.)?
Is the water cloudy at all? Ammonia tends to cause bacteria blooms that cloud water.
Never heard of a clown doing this. If all the fish are at the surface aerate the tank and yes, add bacteria.
@brandon429 may want to check in,
Yes API, But it has been reading constantly 0 for several weeks so it seems something has changed. It’s just one of the 2 clowns, the other isnt doing it, neither is the orchid dottyback.
Water is crystal clear at the minute..