Small fish that picks at substrate and algae?

So I have a 9 gallon nano (livestock below), and am looking for a 3rd and final fish to round out the tank. I'd like to get something smaller that will pick at some algae and do some cleaning/moving around of the substrate in the tank. Maybe pick up some of the smaller algae bits growing down there. The lawnmower blenny I have doesn't do a whole lot of lawnmowin', unfortunately. He only wants straight fish food...even after not feeding him for a few days. I have only seen him peck at the rock a few times over a couple weeks. What a jerk. I know I can't get another blenny or goby since my guy will probably try to fight it, right?

Any recommendations? Something colorful would be a good plus, obviously :)

Livestock:

Flame Scallop
Feather duster
Peppermint Shrimp
Pom Pom crab
Oce Clown
Lawnmower Blenny
4 Astrea
4 blue-leg hermits