Clownfish

[RockoBuffone]

What are my clownfish genders

 

[ISpeakForTheSeas]

What are my clownfish genders

Assuming you only have two clownfish, and assuming that they’re mature (i.e. adults, not juveniles) the big one would be female, and the smaller one(s) would be male (they’re protandrous hermaphrodites, and the dominant [read: bigger] one in a pair/harem is female; to my understanding, lone clownfish turn female too).

Welcome to Reef2Reef!

 

[Rugops]

If they are the same size, the more aggressive one may cause the one being harassed to change gender.