Goldfish like to explore and put everything in their mouths. This includes food, soil, plants and other fish. Because of that, it is important to avoid any species that are small enough to fit in their mouths.
When choosing tankmates, you must consider the size of a full-grown goldfish. For safety, match similar sized fish within 25 percent. Some people notice that goldfish seem to like to take everything what they can fit in their mouth do not put fish of very different sizes in a tank.
How to Choose Tankmates for Goldfish
Goldfish can live with other fish that have alike needs and character. They are relatively peaceful, but they will eat smaller fish. On the other hand they can be bullied by same-sized species.
Finding proper companions for goldfish can be hard. Many species fit, if you follow advice exactly. Good choices for an aquatic group include danios, minnows and snails.
Snails are great if you want to avoid cleaning works. Between compatible coldwater species are white cloud minnows, hillstream loaches, and some big coldwater plecos. White cloud minnows are little and active, although they require groups and stable cool water.
Hillstream loaches also fit.
Temperature matters a lot for choosing tankmates. Goldfish are coldwater fish that require permanent heat between 65 and 75 degrees. Because of that they never coincide with tropical fish that requires warmer water.
Goldfish should not live in a discus tank, because they do not last such high temperatures. Tank temperature can be room or tropical. Room can reach the 60s or even 76F, while tropical start at about 76F. Fancy goldfish like warmer water, while comet goldfish favor cooler temperatures.
Average goldfish, similarly to comets, live with species of same size and water temperature.
Space matters for goldfish. They require a lot of room, and adding other species requires even more space. A 10 gallon tank barely enough for one goldfish to live a long, happy life.
A single goldfish ideally require 150 gallons or more when it fully grew or live in a pond. Some advise at least 40 gallons each fish. Adding more species, the tank must be quite big to avoid overstocking.
If a tank is too small, it quickly will overloaed.
