Did you check the hose running from the overflow to the sump. I once had a fish stuck in there, had to cut a perfectly fine hose to rescue him

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Hmmm. That might be a possibility, but the wrasse is slim/narrow and the hose quite wide. The flow does go quite strong during peak DC pump settings, so he should have gotten flushed by now.
They do hide in the tightest corners. Last time I found him in Sump Overflow box, but I never saw him at first glance. Took a strong flashlight to notice him in there.
So I do have to start some serious looking. Beyond just a peek, here and there.
Time is running out, unless he is feeding off of leftovers going thru return system (Somewhere!!)
He was nicely fed and plump before he disappeared so I'm assuming they won't starve that quickly.
GOING TO TRY THIS
This Dlink WEB Cam with (TimeLapse Photo capture, Night Vision and Motion Sensor trigger) has been very useful many time.
Found our LOST Hamster, Mice in the house, Squirel doing damage in backyard, etc.
So I set it up for 1 minute snapshots, 24 hours, and Infared-Night Vision.
Motion sensing won't work since too much activity in sump.
But if he comes out, I'll see him (will save me a sump tear apart)