Compatibility: Goldfish are not always compatible with other fish species. They can be boisterous and may nip at the fins of slower-moving or more delicate fish. Some species of fish, such as barbs and tetras, may also outcompete goldfish for food.
Water Quality: Goldfish require specific water conditions that may not be suitable for other fish. Goldfish prefer cooler water temperatures, while many tropical fish require warmer water. Goldfish also produce a lot of waste, which can quickly deteriorate water quality if the tank is not properly filtered and maintained.
Disease Transmission: Goldfish are susceptible to a variety of diseases and parasites that can be transmitted to other fish. Keeping goldfish with other species increases the risk of disease outbreaks and can be detrimental to the health of the entire aquarium.
Stress: Mixing goldfish with other fish can be stressful for both parties involved. Goldfish prefer peaceful environments, while many other fish species may be more active or aggressive. This can lead to increased stress levels and negatively impact the overall health and well-being of both goldfish and other fish.
For these reasons, it is usually best to keep goldfish in a species-only aquarium or in a carefully selected community tank with suitable tankmates that are compatible with the water requirements and temperament of goldfish.