What have you done as far a changes to your tank since the outbreak, the main things would be lighting, good water flow and maintenance, keeping filters clean and reducing nutrients thru regular water changes. keep in mind that snails, hermits, fish will only eat whats natural food for them, green hair algae is not one of them at least not the kind that grows in dead water areas in a reef tank. I still had that algea on top of powerheads, and in a dead area without waterflow, I recently added a refugium (for other reasons) with macro algae and most of it is gone the powerheads are clean. I have a few hermits, they are fun to watch but I would look at your tank and equip as the source and the solution to any algea problems