Blennies are good but they're grazers and will eat what you feed your (frozen, etc.) this limiting their algae appetite. In a larger tank algae will probably grow faster than your blenny can handle. On the other hand you have sea hares which take to algae like a t-800 to John Connor. I have a 75 that had a decent hair algae issue bought a medium sea hare and it was completely gone in 2-1/2 days. They literally do not stop eating. The down side is once their out of food you need a new home for them. We had a couple years back one that traveled from tank to tank in my home town. One side note be careful if you have cleaner shrimp, since they clean any new addition to your tank they'll go straight for him. Bad part is even though they're trying to help they can easily kill him by over picking at his rectum and tearing it.
