The outdoor pond in your yard will let you observe your goldfish in a natural setting. In establishing and maintaining a goldfish pond, be aware that the aquatic habitat needs of goldfish species vary. Some are tolerant of temperature changes, others are not. Also, not all species make good pond mates: Some species do not swim well with others.
Fantail goldfish are some of the best species of fish for beginners looking to establish a home- or office-based aquarium due to their long, flowing fins, hardy constitution and general ease of care, according to ExoticGoldfish.net. They are generally a peaceful breed but certain circumstances can bring out their aggressive side. Hunger, stress and a desire to mate can incite them to chase each other in a quest for dominance.