i tried several types of algea eating fish, crabs, snails, etc. when i was having serious biprosis (Not sure if i spelled that correctly) algea (and i also had a couple other kinds of algea) issues. unfortunatly nothing was that effective for correcting a problem but they probably work great for maintaining the tank once any serious algea issues are resolved. i had to ultimately get a phosbane reactor (used "rowaphos" media, tried "aquamax gfo" but it wasnt effective enough), and i had to actually pull the most problematic rocks and scrub them clean with a hard bristle toothbrush and wash with saltwater (claimed from the tanks last water change, then flushed off with clean saltwater several times). finally got on top of it and have no more issues, it was a bit** getting rid of tho. good luck! (Ps. i noticed a "slug" i put in there actually maintains the tank really awesome, eats way more algea than any fish i ever put in there