Lawnmower blenny wont eat

I recently lost my lawn mower blenny in a overflow accident so fixed
the problem and decided to get a new one. Problem is this new one
dosent seem to want to eat. Its been in the tank about a month and I
havent seen it eat once. I've tried broccoli and brussel sprouts(my
old blenny loved these) nori and frozen Formula One. These foods plus
algae occuring in the tank were more than enough to fatten my last
blenny but this one hides most of the time and is now looking weak.

A guy at the LFS told me it IS eating whether I see it or not and just
to wait, but I think this fish is a goner now. Anyone have any
suggestion on what I should do or any foods I should try?

Thanks,
Matt