Nope, he doesn't mess with anything. Not even the algae!! He's spoiled and will only eat the most expensive Sea Veggies. I got some new corals today to fill those open spaces, I got a small trumpet coral and a small short tentacle plate coral for the bottom and a really big pineapple brain. So big I'm having a hard time finding a place to put it... And I got this really pretty turqoise mushroom (a color I've never seen one in before, it was very unique looking) that promptly fell into a 6 inch deep hole in one of my rocks. I tried to fish it out using tweezers, and then a gravel vacuum, but I'm afraid it's off to the land of Jermy's blue xenia...