Tetra Pond AlgoFin. For effective and safe destruction of stubborn filamentous algae and other algae in the garden pond. Optimal supplement for further algae prevention: Tetra Pond AlgoProtection and Tetra Pond PhosphateMinus. Works in 2-3 weeks & prevents algae formation. Compatible with aquatic plants, fish & micro-organisms if used correctly. Particularly easy & precise to dose.