I had the same thing happen about a month ago....I immediately did the same thing...posted my concern on Maast! I'm happy to say that mine has fully recovered and he looked way worse than yours in your pic. I think I need to go to a closed loop. My Maxi Jets no only look unsightly but have recently injured my blue linkia star fish....poor thing lost the tip of a leg about two weeks ago but is still kickin'!

Best of luck, I hope he recovers!