I am going out of town on Thurs. so I need help fast. I have had a pencil urchin for many years. I recently added corals to my tank so he became a problem....mostly with knocking the corals over or knocking something over on them. I moved him into my tank that has fish only (well actually, shrimp, hitchhiker sponges and some xenia, too), thinking he would do well there. He has been fine for @ a month. A few days ago, after I cleaned the algae off the back of the tank, I noticed he was parked on top of my biggest sponge &, because he had grazed over him before and got him looking pretty clean, I thought that he (the sponge) would be looking really nice & yellow when the urchin moved on. Finally,( he was just there too long) I moved the urchin myself... AND, you got it, my sponge was GONE! I really didn't know that urchins would eat a sponge! I have some more sponge that is yellow but is not really in a shape... just grows on live rock in splotches- and he's never bothered that either. I didn't purchase any of the sponges.... they came in on some live rock & have grown pretty well- which made them extra special! After I moved him he went in the opposite direction and I thought the other 2 smaller round sponges would be ok. Today, I checked him (for the millionth time) & he was on the other sponge. When I pulled him off, the sponge was @ 1/4 gone. I don't want to get rid of him & honestly, I did clean the algae off of the back of the aquarium so he may have been really hungry. I have a floating baby fish box net thing that I have over the remaining sponges held down with a rock. Do you think that will protect them until I get back on Monday? I'm thinking of leaving the lights on all night to get some algae growing again for the urchin. I'm attached to the urchin but he's been causing lots of trouble lately so I realize I may need to get rid of him. What do you think? Is there any other way to protect the remaining 1 3/4 sponges and keep the urchin? Oh, & will the others grow back? I think there might be a little left of the large one...very little... but I do see a little yellow left on the rock. The smaller sponge looks like his top has just been sliced off... very clean. I don't know much about sponges but it looks like there are obvious layers inside -which is interesting. Should I try to remove what is left or hope he will grow back? Please inform.... I'd like to keep them both (urchin & sponge)... but will sadly give him up if I have to. Oh, should I leave the box net thing over the sponges? Will they be ok until Monday?