ISTA Multi algae scraper Cleaner - Aquarium Fish Tank ISTA Multi- scraper Cautions:Be aware of sharp blade!Please retract the blade after use. Operation:press the two convex of scraper and extend it forwardly is stainless steel scraper.Press the two convex of scraper and retract it backwardly is rubber scraper.Connect with ISTA water vacuum cleaner can scrap off and move out algae and dirt from the tank bottom.