I had two otos in my tank, but one has been missing for a couple of days. Thought he might have passed away, but no body to be seen. Same thing happened with my third one a few weeks back so I wasn't overly surprised.
Then today I saw its tail below the heater. Thought it was on the glass by the heater, its usual favourite spot. But no. The heater fits into a little sort of cup which in turn attachs to a sucker to stick to the glass (hope this is making sense). The little cup has slits in it, and the oto had wriggled in and apparently got stuck
I assumed he was dead so took out the heater to remove the body, but as I did so, I could hear him thrashing around
So I quickly put it back into the water, pulled the cup bit off the end of the heater, and off swam my oto 
He is now happily stuck to the glass. He looks a bit thin but otherwise OK I think.
Then today I saw its tail below the heater. Thought it was on the glass by the heater, its usual favourite spot. But no. The heater fits into a little sort of cup which in turn attachs to a sucker to stick to the glass (hope this is making sense). The little cup has slits in it, and the oto had wriggled in and apparently got stuck
I assumed he was dead so took out the heater to remove the body, but as I did so, I could hear him thrashing around
So I quickly put it back into the water, pulled the cup bit off the end of the heater, and off swam my oto He is now happily stuck to the glass. He looks a bit thin but otherwise OK I think.
its suprising where they manage to get stuck
