THESE ARE FANTASTIC ALGAE EATERS!!
Sea Hares are hair algae mowers, they eat vast amounts of algae. They are quite hardy and do well in all marine aquariums, however if significantly disturbed they will release an ink-like substance. We have not found this to be of any consequence to any of the tank's inhabitants. If they deplete the algae growth in the tank, then supplement their diet with Nori.
If you have a hair algae problem in your tank these will clean up and control it!