Newa Aqua Algo Prevent Filter Cartridge a replacement cartridge to prevent phosphate build up in the larger Newa Filters. Each cartridge contains synthetic resin with a highly porous surface that absorbs Phosphates and Silicates. It\'s specifically designed structure ensures excellent contact with water, optimizing filtration performance. When used continuously it is highly effective at controlling pollution within aquariums caused by an excessive build up of phosphates. Phosphates are the main catalyst for unwanted algae and so preventing a build up significantly improves living conditions within the aquarium. This cartridge fits easily into the Cobra 130 & 175 and Duetto 50, 100 & 150. Each pack contains 2 cartridges which will last approximately 3-4 weeks per cartridge. Suitable For: Freshwater. Marine. Reef.