Heard splashing and ran to the tank. Tiger my escapist kuhli had wriggled past the pantyhose barrier and was trapped on the lip of the HOB under the wheel. At least once he was there didn't want to swim 'upstream' anymore but seemed frantic to get back in the tank. I don't know how to pull it any tighter without tearing- and its flexible so a bit of sag in the middle where the flow pushes it- probably where he got in.
I put the thin panel of coarse sponge back on. There is one other benefit to this- it gentles the flow enough that my aponogetons don't get blown around but keep their leaves standing more upright they way they get arranged when I fluff them with my hands during cleaning. It looks nice.
But I worry that with less surface motion my hillstream loach may feel oxygen deprived.