It would really help if you could tell us what kind of algae you are having an issue with. There are a lot of algae eaters for saltwater tanks but as said above, many only eat a certain kind of algae so just getting any may not help with your problem if they may not eat the algae, you have an issue with.
Hermit crabs I know do eat all kinds of algae but that would depend on if you were able to have those in your tank.