With me algae blenny will only eat algae in the system on the rocks and sand. I never seen it eat fish food like the other fish. I used to turn off the power heads once every 2 weeks and let the blenny go in graze in the algae that accumulate inside the power heads.
The only algae blenny that does eat is a black algae blenny, forgot what it's called exactly. That one eat frozen food like a pig...
It took a few months before my algae blenny starting eating flake. He will still not eat any meaty foods like brine or calanus. They primarily eat film algae and detritus off rocks.