I almost had a BTA make itself to the power head this morning. I turned it off while I was at work. I got some panty hose and put it around the powerhead. tested it out and got no flow. I can't adjust the speed of the PH since I have the Aqueon Ciculation pump 950. I cut a couple holes in front but still very low flow. I expanded it a little but more and still not much flow. I decided to leave the front wide open. and got good flow. but there was still a problem that the BTA could still get into the front since there was large gaps in the front where it blows the water. I got some egg crate and sip tied it to the front of the power head. although it still has gaps but not nearly as much as there was before. I tested it. I can't even get my pinky finger in there to touch the plastic blade. so I think this will do the trick. if it doesn't i'll double up on the egg crate in front and make the holes smaller.