[minerva]

My tank is not drilled - I have a HOB overflow. When it works, it works well, piping water down to the sump below my tank. The problem is, it regularly gets bubbles stuck in it. That breaks the vaccuum and then I have to clear out the bubbles and create suction again to get it working.

My current 'fix' is putting cotton batting in the entry to the overflow, as that seems to filter out the bubbles. Obviously, it gets clogged up and becomes a nitrite factory and has to be changed every few days - a little more hassle than I'd like.

Is there another soul in the world that uses a HOB overflow? How do you deal with the bubble issue?