That is haddoni. And its as apt to eat the clowns as host them. They are predators and take anything that goes in them. That being said I have seen plenty of clowns being hosted by them just fine They do have very nasty stings and are very hard to get loose from skin. I would definitely wear gloves messing with things around it. All the fish eating and stinging aside they are wonderful creatures to have in a tank provided proper care. They like low flow and medium to high lighting. I feed mine every other day because I want it to grow but some never feed theirs and they do just fine. I feed raw table shrimp. They can grow up to three foot normally in the wild, but most will stay a foot and a half to two foot In a tank depending on feedings. Foot should be buried at the rock/sand interface when it settles down it should open up nicely. Watch for deflating for the next few days. Once settled it should not deflate, if it does repeatedly that's signs of sickness.