During my latest water change, I got the chance of sexing my fishies with the 'anal opening shape" method. Some got clearly the "convex" female opening, some got clearly "concave" male opening, and there are some "flat" opening
Is the method a reliable way to sex young fish (less than 3" long including tail)?

PS: I also tried the pectoral fin thickness method and it seemed to match with the anal opening method.

cheers

Golem, a very experienced fish breeder tells me all the time that the most reliable way is the fin technique. He demonstrates it a lot on his ranchu he brings to shows. He was right with the fish I picked from him....

Hardest thing to do with my fish is to get them to stay still long enuff so i can observe their pectorals

How does one tell by the fins?
*Curious*

I was wondering that too. I just went and looked at my fish that I already know the sex of and I cant see a difference between the male and female by the fins

The leading ray (spine) of the pectoral fin is thicker in male fish.
Also males have more pointy pectorals while females are more rounded. Easy to say but hard when it comes to practice

I agree...my fish are too excited to see me or thinking I'ma feed them....lol

You see, you have to hold them to find out - watching them doesn't always work, not to mention that you could sit there for a long period of time...
If you wonna practice, try it out on a profen male and female, hold them and slide your index finger and thumb alongside their pectoral fins. With a little time, you'll get the hang of it....

LOL ok well howsabout I just pretend as I have from day one that mine is a male

Lol that could work then one day your fish might decide "hey, i wanna be a female instead" and start spraying little white globes all over ur tank

LOL that would certainly shock me

I trained a parrot for a woman some years ago. She named it lucy. I had to inform her that the parrot was in fact male.
His name is now Lou. C LOL

Does the fin technique hold out between species too? I have an oranda and a comet we think might be mating but I havent been home to see the difference in fins.

TastyRamen
yes it should but no matter what aproach you take often it depens on the maturity of the fish.