A filter is an essential part of any aquarium. Some aquariums come already installed with a filter, but some you need to buy alongside. A filter basically cleans the water of debris, removes the toxic buildup of ammonia and nitrates, and aerates the water so your fish can breathe. It is therefore incredibly important you get one with the correct size and power to successfully filter the bad stuff out of your aquarium water, so please let us know if we can assist you in choosing a sufficient filter.