When it comes to a small aquarium, there are several types of fish that are particularly suitable. It is important to choose small, quiet fish with environmental requirements that match the size of the aquarium. Here are some of the popular types:

1. Guppy fish
Features: very colorful fish, easy to handle, and durable. They reproduce easily, so you can always enjoy new offspring.
Requirements: fresh water with a pH between 6.8 and 7.8 and a temperature between 24-28 degrees Celsius.
2. Neon Tetra fish
Features: Beautiful little fish with bright colors. They are social and like to be in groups.
Requirements: fresh water with a pH between 6.0 and 7.0 and a temperature between 22-26 degrees Celsius.
3. Betta fish
Features: Very colorful fish with an independent lifestyle. Be careful not to keep more than one male fish in a small aquarium, because they can be aggressive towards each other.
Requirements: fresh water with a pH between 6.5 and 7.5 and a temperature between 24-28 degrees Celsius.

4. Corydoras
Features: Small and sociable bottom fish. They help keep the aquarium clean by eating leftover food.
Requirements: fresh water with a pH between 6.0 and 7.5 and a temperature between 22-26 degrees Celsius.
5. Rembrandt fish (Endler's Livebearer)
Features: Small and beautiful fish, easy to breed, suitable for small aquariums. They are social and like to be in groups.
Requirements: fresh water with a pH between 6.5 and 7.5 and a temperature between 24-28 degrees Celsius.
6. Pandala fish (Paludarium Fish)
Features: small fish that are suitable for aquariums that are half water and half land. They can swim in water and walk on the surface.
Requirements: fresh water with a pH between 6.5 and 7.5 and a temperature between 22-26 degrees Celsius.

Additional tips
Groups: When choosing social fish, be sure to buy several fish of the same type to keep them social.
Pairing: Make sure the fish you have chosen are compatible with each other and are not aggressive.
Adequate aquarium: Make sure the aquarium is equipped with good filtration and appropriate vegetation to provide a healthy environment.
In a small aquarium, it is important to pay attention to the water quality and environmental conditions. If you take care of it properly, you will be able to enjoy healthy and happy fish!