I have a UGF and have been running both jet heads in my 29 gallon aquarium together because of ich treatment. One head is set to aerate. I got home last night and I see a tail protruding from one of the jet heads. I thought OH NO a loach killed himself! Wondering just as quickly how he got in there against the current, into that TINY hole... I pull the head out of the riser tube, and the loach simply floats out and is obviously still alive. Alive, good. What shape he was in, I didn't know. We go to dinner, I didn't turn the heads back on since I wanted to make sure they weren't malfunctioning first. We get home. I see a tail protruding from the head again. I tap the head until the loach backs out of it and swims off. Then I see it... A snail on the inside of the riser tube. I couldn't believe it but I am sure that is what he was after... 
Take care,
Mary.
Take care,
Mary.