If your goldfish is metallic yellow or orange with white markings, it may be a common or comet goldfish. These are marked by their sharp, forked tail. If your goldfish is metallic yellow or orange but has a double, flowing tail, it may be a veiltail or a fantail. If your goldfish is black with bulging “telescope” eyes, it is probably a black moor. If your fish has calico markings, it is likely a shubunkin. These colors might include orange, white, gray, blue, and yellow with black speckles. [2] X Research source
For most varieties of goldfish, a bronze or brown coloring may indicate that it is under a year old. If it has a gold metallic coloration, it is probably an adult between one or two and ten years of age. [3] X Research source Black Moor juveniles may be silver or dark gray before darkening to black as adults. [4] X Research source Shubunkins will be multiple colors, but blue is often the most prominent color in adults. [5] X Research source Some goldfish begin to turn white as they grow old.
Goldfish with flowing tails or double tails will not have a pronounced caudal fin. These include the veiltail and fantail varieties. Instead of changing shape, its tail will grow in length as it grows older. Veiltail’s caudal fin can grow up to two inches long as an adult. [6] X Research source
If you keep your goldfish in a small bowl, you may find that its growth is stunted. In this case, size may not be a good indicator of maturity. [8] X Research source Some goldfish can grow over 12 inches (30. 5 cm) in length.
Males will develop small white spots on the operculum (gill cover) and the pectoral fin. These white spots are called breeding tubercles. A female’s abdomen will become fuller and rounder when it is ready to breed. [11] X Research source While it is impossible to accurately sex your fish before it has developed these physical characteristics, in general, males tend to be smaller and slimmer than females. [12] X Research source
Some breeds, such as the Black Moor or Shubunkin goldfish, mate only in summer, while the common goldfish can mate at any time of year, provided it has proper tank conditions. [14] X Research source [15] X Research source [16] X Research source Goldfish that live in ponds will typically mate in spring. [17] X Research source
A single common Goldfish should be kept in at least 48 gallons (181. 7 L) of water. Add 14 gallons (53. 0 L) per each additional fish. A single fancy Goldfish can be kept in 36 gallons (136. 3 L) with 12 gallons (45. 4 L) per each additional fish. [20] X Research source
You should replace about 20% of the tank’s water every two weeks to keep the water clean. [22] X Research source A filter in your aquarium will make sure that the water is clean and properly oxygenated.
