One problem is you have a large bioload for that tank. Triggers have hella bioload issues and anemones arent clean critters either. I doubt the trigger would mess with a blenny, but on the same note a blenny will leave the hair algae alone. Never treat the symptoms, go after the problem. Before I go off on having a trigger in such a small tank, here are some things to check.
1. Skimmer, get one rated for at least double the water volume maybe a little more since you have a trigger.
2. Reduce your light hours
3. put a phosphate sponge in your overflow or filtration.
4. Do not feed as much, hard when your critters consist of a trigger and anemone.
I wont bother on the trigger thing because if you cared about the fish in the first place you would have looked it up and seen they were too big for that tank.