Goldfish make a big splash during mating which occurs before dawn and normally in a low light environment. The next thing you will notice is that there will be thousands of eggs scattered everywhere that are sticking onto plants, tank surfaces and the aquarium filter. The only reliable way of characterizing between male and female goldfish is by looking for the presence of white spots appearing on the fin and gills. These spots can only be seen during mating season.
Goldfish are heavy eaters, and they are considered one of the greediest aquarium pet fish. They will eat until they are full and if you decided to add more food, they will continue to eat until they become bloated. This habit is one of the reasons they experience flip over condition. Therefore, do not get deceived by their enthusiastic behavior, which can make you think that they are still hungry.
There are at least 20 known varieties ranging from fancy slow moving delicate goldfish up to the hardy pond dwellers. They all originated from the same species meaning that if they are left together in the same fish tank, they will interbreed to produce off pring that resemble their parents. Some of the popular varieties are Pearlscale, Oranda, Veiltail, Shubunkin and Tosakin.
Goldfish can live up to 20 years if they are well cared for. The most important criteria to ensure that they survive up to that long period is to provide good quality water that remains consistent with their needs. They are cold water fish, not a tropical species, and their water temperature should be within 64-72 degrees F. with a pH of approximately 7.5. Watch out for nitrite and nitrate levels and make sure to keep them at a low level for the healthiest environment.
Goldfish can grow up to almost 12 inches including their fins. The fish that you see in pet store aquariums are juvenile fish. And because of this, never ever put them in fishbowls; a 55-gallon fish tank is an appropriate home for one pair of goldfish.