What types of fish need a filter?

* Fish that produce a lot of waste: Some fish, such as goldfish and cichlids, produce a lot of waste. This waste can quickly build up in the water and cause the water quality to deteriorate. A filter helps to remove this waste from the water and keep the water quality high.

* Fish that are sensitive to water quality: Some fish, such as tetras and rasboras, are sensitive to water quality. They can easily get sick if the water is not clean and clear. A filter helps to keep the water clean and clear and prevents these fish from getting sick.

* Fish that live in a planted tank: Plants need clean water to grow. A filter helps to remove dirt and debris from the water and keeps the water clean for the plants.

* Fish that are kept in a small tank: Small tanks can easily become polluted. A filter helps to keep the water clean and prevents the fish from getting sick.

In general, most fish will benefit from having a filter in their tank. However, there are some fish that do not need a filter, such as bettas and guppies. These fish can live in a small tank without a filter, as long as the water is changed regularly.