Try a green emerald crab. They are small and love to eat green algae of all sorts. I have a 3 gallon pico reef that I've been battling hair and bubble algae with for a while. Did a little research on these crabs and they will devistate bubble algae and green hair algae. I picked one up at my local reef shop and this little fella did the job. Keep an eye on this crab because it also has an appetite for corraline algae. My pico is now algae free and I toss the crab a few pellets of marine two every other day. Astrea snails help also.