Speck with eyelashes

I had this photo filed under "Best copepod so far". It was just another moving speck, maybe a millimetre long, on the inside of my aquarium wall. Nothing unusual; crowds of tiny critters dance along the glass; the larger ones are baby amphipods, and most of the smaller ones are the one-red-eyed copepods. Sometimes one, too tiny for my camera, looks more like a mite.

Tonight, I finally got around to cropping and examining the photo. And it's no copepod that I recognize.

Speck with eyelashes

For one thing, it has two eyes. The shape is right, but the tail is different. A female copepod often carries eggs at the rear, but in two fat sacks, not 4 pointed, hairy ones.

It doesn't look like an amphipod, either; an amphipod usually holds the antennae forward, not off to the sides. It almost always has long hind legs sticking out at odd angles from the back; when the tail end is curved inward, from a front view, it would be nicely rounded, with those legs well out to the side.  The eyes are too small.

I've spent hours looking for one like it.

I give up.

Help! What is this?