Red Sea ReefCan Series 18 is a high-quality, space-efficient reservoir designed for auto top-off (ATO) systems, ensuring a stable water level in your aquarium. With an 18-liter (4.75-gallon) capacity, this durable and compact ATO reservoir is perfect for maintaining consistent salinity and water chemistry in both marine and freshwater aquariums. Its sleek design fits neatly inside or next to aquarium cabinets, offering a hassle-free solution for evaporation management.