How do you determine the sex of goldfish?

Answer 1

Look under the fin!!!

Answer 2

Want to be able to tell the sex of your Goldfish? At one glance, they all look the same right? Wrong! If you want to breed goldfishes, you better not have all males in the tank.

Following are some methods that can be used to recognize the sexes but even these are useless unless the fish are at least a year old, i.e., have attained sexual maturity.

1. Midline ridge: male goldfish have a ridge running through the back of pelvic fins to their vent opening on the underside. The ridge is either completely missing or smaller in females.

2. Firmness of abdomen: The area between pelvic and anal fins is pliable for females but very firm for males.

3. Shape of the vent: Though difficult to figure out, the female vent is rounder and convex, whereas the male vent is thinner and concave.

4. Shape of the pectoral fins: Male pectoral fins are pointed with stiffer leading ray and female pectorals are rounded, shorter with finer front fin ray.

5. Features: females are brighter colored and are more active. This could be a difficult way of pointing out a female but you could try!

6. Check out: One theory says that you can introduce a known female into the tank and watch for the reaction of fish. Males will check out the new fish but the females will show no interest!

The only way you can learn to spot male and female goldfish is by closely observing known males and females and noticing their various traits. A pet shop could be a nice place to learn this.

During spawning season it will be easier because the male will follow and nudge the female relentlessly sometimes even bruising and injuring the female. Finally, it’s only your experience that will give you any degree of confidence of judging the sexes by looking at them in a tank. Difficult but definitely not impossible!

so there are ways but it takes a while to get it right .. good luck!!!
also here is a good link

Answer 3

First, sexing young and juvenile goldfish is virtually impossible, you have to wait until the fish reach breeding age (usually one year old). Secondly, sexing adult goldfish out of the breeding season is difficult, because the sexually distinguishing features only develop during the breeding season (in the spring time). That said, females may be deeper in the body than males. During the breeding season, the following physical features develop: males develop breeding tubercles (white pimples) on the gill covers and on the leading edge of the pectoral fins females develop a deeper body as they fill with roe (eggs), and have a larger vent (just before the anal fin) than the males. All this said, it sounds a lot easier than it really is. The difference between a convex or concave vent is minute as are the tubercles, so making these determinations is still difficult.

Answer 4

Best I can tell you is watch for the ones that get pregnant, those will be the females. Once you know which is which, I believe careful observation may yield further clues.

Answer 5

Ya don't. Can't tell by looking.