I found a couple of strange, wiggly creatures in my tanks this morning, and after catching, examining, and research, I've got mosquito larva and pupa in my tank! Not totally unheard of, since my room is right my the front door, and I do get the occasional bloodsucker in there. My plan is to increase the power in the filter, and scoop them up as I see them, since the pupa tend to hang out at the surface. If it gets too bad I'll put a platy in there.