The Tetra EasyCrystal Filter 250 is used for mechanical, chemical and biological water treatment in aquariums with a volume of 15-40 litres and is intended for use in freshwater aquariums.nFor the well-being of your fish and plants, permanent filtering of the aquarium water is necessary. Tetra filter technology safely breaks down excess nutrients and thus ensures permanently good water quality. The filter is the heart of every aquarium and is therefore chosen to fit every biotope. It is not only the size of the tank that is important, but also its inhabitants. At Tetra, all AquaArt complete sets contain the right filter for the fish stock suitable for the respective aquarium. However, if the circumstances change because the fish are multiplying or very small animals such as dwarf shrimp are feeding in, the existing filter may also have to be replaced by a more suitable one. Here Tetra offers a variety of devices that are suitable for all tank residents and aquarium sizes.nThe Tetra.