Is It A Boy or A Girl?

It’s not easy to tell the sexes apart in goldfish. The males don’t get into fights and the females don’t have markedly different colours like a lot of other animals, so it requires a bit of care and looking closely to find out which goldfish is male and which is female.

Breeding Signs

The best time to tell male goldfish from female goldfish is the breeding season i.e. Spring. This is when the male goldfish will develop small white pimples (sometimes called tubercles) on the outside of the gill flap, and along the front edge of their pectoral fins (these are the ones just below the gills).

Also at this time of year the female goldfish will get a bit fatter because she is full of goldfish eggs (properly called roe). However, please don’t assume that a heavier looking body means a goldfish can be called Mummy. It could be a symptom of illness or disease, so look out for other signs of trouble.

The Vent

The vent is the opening at the rear end of every goldfish that is used for defecating and reproduction. In female goldfish it is a round-ish shape and is slightly raised above the level of the skin. The male goldfish’s vent is usually more oval in shape and does not protrude as much.

Be aware however that like most methods of sexing goldfish, comparing vents cannot be done at a glance. A bit of experience and careful examination is required.

Midline Ridge

Male goldfish often have a ridge that runs along the back half of their underside ending at the vent. This feature is usually absent in female goldfish, but can be present and should only be used as confirmation of other observations.


In the breeding season male goldfish chase female goldfish. Out of the breeding season male goldfish chase male goldfish. Therefore to use this method of sexing it is vital to have closely observed the goldfish for a period of time before making any decisions.


With experience and careful observation it is possible to learn how to tell male and female goldfish apart by the thickness of their anal fins, the shape of their pectoral fins and the firmness of their abdomens. Some people have even claimed to be able to tell them apart by colour. However, these methods can only be used with any degree of confidence after years of experience of keeping goldfish.


Wait until goldfish are mature before attempting to find out what sex they are. It is very hard to tell outside the breeding season without a great deal of experience. However, taken together the signs detailed above can lead to a definitive answer.

26 Responses to “Is It A Boy or A Girl?”

  1. Tonya Says:

    thankyou for that info. my little 8year old wanted to be a vet. of all types of animals bye.

  2. gina Says:

    Thanks very MUCH for this insight into sexing of goldfish! I have a comet; a fantail and a black moor, and they are exhibiting signs of spawning…as it is Spring and the ‘male’ appears to be chasing the ‘females’ 🙂 I had heard about the underside ridge before, and was not sure what to think, but now that I have read this, I feel a bit more satisfied. Thanks again!

  3. Hailey Says:

    Have anyone here tried feeding their goldfish with live foods? What live foods have you tried for your pet?

  4. tamera Says:

    thank you im getting a goldfish and if i get a girl im naming it wanda boy its gonna be goldie

  5. joey Says:

    also you can tell by getting a top-view and females are wonky to 1 side, while males are more straight.

  6. taylor Says:

    this sucks i cant tell my wether my goldfish is a boy or girl cause i only have one so theres no breeding no chasing so idk what to do

  7. amy Says:

    i gat a new fish i won at the fair and i wanna know if its a girl or boy i want answers but im confused my fish is silver with gold spots!

  8. Savannah Says:

    Thank you very much I have been seing my goldfish have been chasing and rubbing up against eachother but to find out… they are all males… so now I am going to find a female and put her and annother femail in the tank and see what happens… once again, Thank You!

  9. YS Says:

    thanks, but i still cant tell the difference
    one chases the other quite often and never the other way around but this in in late august what does that mean???????

  10. Violet Says:

    Hi everyone i just got two fish and i saw this video on youtube about fish mating and i thought i might have a 100 little tiny babies swimming around in my tank because my fish were chasing around each other and it is mid-summer i started to get all paniky thanks so much now i can sleep soundly but it is still really nhard to tell them apart please send me some more info it is so frustrating

  11. kathy Says:

    thanks a lot i want to mate my goldfish and now i know i have a boy and a girl!

  12. hi Says:

    I am going to be vet to when I grow up and thank you for the information

  13. stephanie Says:

    thankyou so much for the imformation!!!!!!!!!!!!!=)

  14. diana Says:

    I have 3 goldfish and one of them is really really fat but im not sure if it’s pregnant or if it’s a boy or girl but I have noticed the other goldfish chases the fat one around alot but im still not sure if she’s pregnant please help this is so frustrating.

  15. diana Says:

    P.S. thanks for all the info

  16. Ruby Cookie Blue Says:

    My female fish has a mini and my male fish has a willy.
    I wish it was that simple.

  17. rachel Says:

    i dont know if my fish is a girl or a boy can you help me it has white fins

  18. Mina Deza Says:

    oh and in says that males are silver and girls are gold is that true?

  19. miah Says:

    um i have the same problem like amy and i want to know how old mine is.

  20. Rebby Says:

    I have four huge fish and eleven feederfish and the huge fish got stuck in the decoration hole and it looked like my two huge fish wre frenching:) yum lol jk but my feeder fish have been going in there and acting like it’s a sex house and u don’t know which one is boy or girl and they keep going in there and it’s like they never come out so my tank looks empty and when I clean it and take it off of them it looks like a volcano blew up because they scatter around and act stupid:p but I love my fish so thanks for the help Ifyou choose to help me out.

  21. chloe Says:

    HEY!!! i am really frustrated i got a fish from church and i have read sooo many articles about it i still don’t know :0

  22. coolchikcuziloveme Says:

    thank you, this is really helpful, i now know i have a white female and a orange male, the male chased after the female and they always seemed together after then but my female pooped out 2 babies and died and im not sure if my fish is very happy, it sits in the corner of the tank all day, so i got him a bigger tank witch i thought he would enjoy but he just sat in his shady patch all of the time and he seemed depressed and not long after he died, about a week after my female died, it wasnt too good and then my babies went a day after thair father, it really is sad (R.I.P. crunchie and rolo, both my babies). i now have 4 females and 1 male with about 8 little fish, so cute and im happy that my new fish are gettng along and are ok. i also work at markets selling them and some other ish breeds and life is good exept we lost one little baby fish out of the family called chloe, a strange name for a fish but i love it (R.I.P. chloe) anyway thank you again and thank you even more if you are going to reply to my message !! x 😉

  23. Alice Says:

    I have two Black moor goldfish and i’m afraid they might breed, I don’t know what their genders are… I have no idea how to take care of goldfish babies…

  24. aaliyah Says:

    only have one goldfish so how do i tell 🙁

  25. brooke Says:

    i just got two fantailed gold fish i cant tell if there a boy or a girl so please help one has a white and orange tail but the others is just orange please tell me and one is bigger then the other????? <3<3 please help<3<3

  26. Susy Says:

    you can NOT sex goldfish just by looking at the color because that isn’t how it is! it said so at the BEGINNING OF THE ARTICLE. Female and Male goldfish CAN have the same coloring as each other so that isnt true Mina.

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