Genetics of Calico Fantail Goldfish

I have always been fascinated with genetics. Although I am by no means an expert, breeding goldfish does have its benefits to see the affects of genetics. There are three categories of goldfish, metallic, matt and nacreous.

Nacreous Scaled Fantail Goldfish baby

Metallic: These fish have a lot of guanine present. Their scales are highly reflective and they look like metal in the sunlight. Metallic goldfish have two dominant genes, lets say SS.

Matt: These fish appear to have translucent or flat coloured scales. There is no reflective colouration. Matt goldfish, which are white and lack colour have to recessive genes, lets say ss.

Nacreous: This is a fish with a mix of translucent and reflective scales. Nacreous goldfish have the genes, Ss.

Most calico goldfish are nacreous goldfish, they have undertones of colour in their skin under the translucent scales and other colours in the reflective scales.

In the recent breeding, I spawned two nacreous goldfish. The resulting fry by these predictions should be as follows:

               S              s


S           SS              Ss


s            Ss              ss

This means there is a 25% chance of metallic goldfish, 25% chance of matt goldfish, and 50% chance of nacreous goldfish.

In my spawning, 60% are nacreous goldfish and 40% are matt goldfish. Now these numbers are different than predicted, but considering the fact that I selected only the two-tailed fry, these numbers are possible.

I have not yet considered the affects of colour, but from looking at the nacreous goldfish babies, they seem to be an even split between the parents.

Now, matt goldfish tend to be less impervious to cold weather, I hope they last the winter, since they are very beautiful babies.