Sea Hare split?
 

I just got a blue spotted sea hare the other day and after a water change today i noticed that a slit running down the center of its back (starting behind its head) opened up. The slit opens and closes regulaly like its "breathing" Does anyone have any experience with these, is this normal? It is still attached to my rock and is moving around.

Thanks,
Derek

Yes it is perfectly normal.

Thought so, did want to stress it out and remove it unless it was dying. Thanks

Well it turns out it wasn't so normal. It inked my tank and died. I havent lost anything else yet due to the inking, but i'll know better when the lights come on.