Posted by Thomas Woelfel on April 24, 2007

Q: Hi, my class just got a new goldfish. We want to give it the right name. But, we can't decide whether our fish is a boy or a girl. Ccan you help us out? What features should we look for to confirm that "Goldy" is either a she or a he? Thanks. Tom

State: New York

A: This is a valid question and one that many fish enthusiasts wrestle with when raising fish, I know I have. Unfortunately, goldfish are more difficult to sex than some other species. IN GENERAL, however, if you have a large assortment of the same kind of adult goldfish (there are many different varieties) all living together and all about the same size and age, those that are a bit heavier (their bellies are more rounded) are likely to be females while the males will tend to be slimmer. This is a general rule that works best when you have many fish for comparison. There is a good chance that your store-bought fish isn't an adult yet which will probably mean it isn't going to show much variation in size one way or the other. I guess if I were you, I'd name your fish something that can be either a girl or boy name and avoid the problem altogether.

If at all possible, your local pet store should have one of those thin, paperback books on goldfish care that should help with care of your fish as well as some basic information on the sexes.

Wish I could give you a definite answer but I'm afraid I can't on this. In any case, I have always enjoyed goldfish and and hope you and the students will too.

John Wiessinger ( April 25, 2007)