The TetraTec EX600 external filter is suitable for aquariums of 60-120 litres. TetraTec EX filters are robust, easy-to-use, and offer state of the art technology at great value. They offer superior filtration over traditional filters, helping to make maintaining your aquarium easier, and improving the environment for your fish. Key benefits The TetraTec EX filters have been designed with ease of maintenance in mind. They not only offer excellent filtration, but are simple to dismantle and reassemble during cleaning. Media: 1) TetraTec CR Ceramic Filter Rings remove large particles of waste, and help to even out the flow of water through the filter. They can be cleaned with tap water and do not need regular replacement. 2) TetraTec BF Biological Filter Foam doubles as a media for removing finer particles of solid waste, as well as providing a high surface area for bacterial activity. To operate the foams purely as a mechanical media for solid waste removal, clean them under tap water as necessary. To maximise their biological activity, clean them in a jug of aquarium water. Our recommendation is to use foam 2.a. as a mechanical media, leaving foams 2.b. as biological ones. 3) TetraTec BB Bio Filter Balls are a specific biological media, providing an excellent environment for friendly bacteria to break down ammonia into harmless nitrate. Because they are not too porous they allow a good flow of water through them, which ensures that all the bacteria receive a supply of oxygen and nutrients. This keeps them working effectively, and avoids ‘dead areas’. Clean in aquarium water only, as and when necessary. 4) TetraTec CF Carbon removes organic contaminants, reduces odours, and prevents the water from going yellow. Its use will keep the water looking like new, as well as improving its quality for your fish. Carbon should be replaced every 4 to 6 weeks, as over time it becomes saturated. 5) TetraTec FF Filter Floss reliably removes very fine particles of waste, thus helping to give the water leaving the filter a final ‘polish’. This, coupled with the carbon, ensures the aquarium remains crystal clear. TetraTec FF Filter Floss should be replaced when it becomes dirty.