Are Sea Hares deadly

I can not remember if seahares are deadly when they die or was it seacucumbers? I have a Falco Hawkfish in my old 20 gallon. He's pretty aggressive. Had a chromis for dinner two days ago. Mmmm.
Seahares are pretty good with hair algae. My crops are growing on rocks I cana't move to the tang/anglefish, blennie tank. Any experiences with them?

Cucumbers can be deadly...

Seahares are very fragile though. I lost 3 before giving up on them.

I've had zero experience with them myself but from what I've read, they are really touchy and if they avoid power head intakes and such long enough to eat your algae, they die shortly after.

So, so far it looks like sea hares are a no go. I was reading on the sea lettuce slug and they could be better, but only if you get a certain species, which can only be identified by an expert. Which I am not...