Many fishkeepers started out with a Goldfish in a bowl or small aquarium without a filter. Whilst it is possible to keep fish without a filter, water quality & clarity will always be a problem. This will also means the water needs changing frequently to maintain an acceptable water quality standard for the aquariums inhabitants. The installation of a filter will reduce the frequency for water changes as well as improving the environment for the fish. Therefore, a filter is essential in our opinion.