The common goldfish is the simplest variation of all goldfish breeds and the fish that most resembles its carp ancestors.
They come in a variety of colors, ranging from red, yellow and orange to bronze and black.
Common goldfish are sometimes confused with the comet goldfish. However, the comet has much longer fins and a longer and more deeply forked tail fin. The common variety also has a more blunt and rounded head.
Temperament and care
The common goldfish is one of the hardiest species of freshwater aquarium fish. It’s therefore an ideal fish for beginners.
Commons can tolerate quite low water temperatures and can even survive for brief periods in frozen-over ponds, provided they have enough oxygen and food. They can also be raised with koi, but should not be kept with slower varieties of goldfish, as they will out-swim and out-compete their slower counterparts for food.
They’re certainly not finicky eaters and will devour almost any type of food provided. They are active foragers and will keep scouring the bottom of the aquarium for food. This should be taken into account when aquascaping and deciding on a filtration system. Goldfish produce a significant amount of waste so an adequate filtration system is a must.
Breeding common goldfish
Given adequate space and food, goldfish will spawn quite readily and prolifically. In fact, it is quite ordinary for common goldfish to overpopulate a pond within a few months of being introduced!
In the wild, goldfish usually spawn during warmer months of the year. Breeding can therefore be induced by lowering and then gradually raising the water temperature of a pond or aquarium. Goldfish devour their own young and eggs, so spawning mats or a heavily planted aquarium (where fry can hide) is recommended if you want the fry to survive.
Choosing common goldfish
When buying your fish, it’s important to pay attention to the basics, such as health and deformities.
The ideal characteristics of a common goldfish include a body depth of 3/8 of the body’s length and a tapered off mouth, which leads smoothly into the curve of the back and stomach.
The fins of the common goldfish should be single and slightly rounded, except for the pectoral and pelvic fins. All fins should be rigid and the tail fin should be rounded and less than 1/3 of the length of the body.