The last three nights, I woke up to find my prefilters out of place. Initially, I just figured the pleco had knocked them down. Last night, it happened again and I observed the pleco swimming along while sucking the glass. I moved the one little filter over so the prefilter woukdnt fall off so easily. I also observed the pleco trying to squeeze behind the intake tube of the aquaclear 110 intake. I think he damaged himself doing it as he appears to have discoloration in areas around his head that correspond to where he's rubbing. I had seen damage two nights ago. I thought he might be trying to swim in the stream of the new powerhead so I moved it towards the front of the tank. As i said, last night he kept doing it despite moving the powerhead. Just tried shutting off the powerhead right and he's still doing it. As I was about to post it, I saw he got the bottom piece off and is just sitting behind it. I did a water change yesterday when I noticed the damage to try to make sure water is clean to allow it to heal. Initially I thought he was enjoying the stream and figured he'd swim on the front glass once I got another powerhead (I planned on two to create more current for the clown loaches). Now I'm not sure what to do. I'm going to test the water but it have been zero everything the last two times I checked it this week. I think the powerhead is a factor as he only started doing it after I got the powerhead on Thursday. BTW, after he knocked off that Aquaclear 110, he stopped pushing there and went to the wood to suck, and now he's sucking on the sponge filter. I still have the powerhead turned off. Thanks for any advice.