Nothing is really reliable if you focus on one sign. You need to take multiple into account and even that is a best guess. I have talked to people and seen thier male rams that have pink bellies, confirmed males as they have paired and spawned. The only sure fire 100% way is to have it pair up and spawn, other than that its a best guess. You however can be fairly certain if it has multiple male/female traits. The ram in question is most likely female due to the fact that it has most if not all the female traits.