Determining the sex of a discus fish is not an easy task. There are a lot of different opinions online about how to determine the sex of a discus fish.
When discus fish are small under 4 inches in size their dorsal (back) fin are always rounded. Therefore it is impossible to tell if a young discus under 4 inches in size is male or female! If anyone that is selling discus claims to know male versus female and the fish is under 4 inches in size- they are probably lying to make a quick sale!
When a discus reaches 4 inches of size or larger the shape of the dorsal fin changes.
If dorsal fin is rounded on the corners = FEMALE
If dorsal fine is pointed on the corners – MALE
Also- a male discus is always larger than the female.
The shape of the dorsal fin is a good indicator of sex but not always 100% accurate.
The only true 100% accurate way to know determine sex of a discus fish is to actually witness them spawning.
The fish that lays eggs is obviously the female.
The fish that swims over the eggs after they have been laid is the male.
If you have a discus lay eggs but the eggs never hatch there is a good chance that you have 2 female discus.
At Discusguy.com we never guarantee the sex of a discus regardless of their size unless we actually witness them spawning.
If you are looking to purchase a discus breeding pair be extremely careful and ask yourself and the sellers these questions:
1- If the pair is successfully spawning and producing fry why would they be selling them?
2- How old is the pair? The older the pair the less likely they will spawn.
3- How often to they spawn? If a pair spawns on a regular basis to produce fry to sell, the female may get burnt out and her health may be at risk. Reputable breeders make sure to give breeding pairs a break in between spawns in an effort not to jeopardize the health of the fish.
4- Where did the discus come from? Were they imported? Local breeder?
5- How many successful spawns have the pair had?
6- Why do they want to sell them in the first place?
7- Are they a PROVEN pair? If so, ask to see pictures of them spawning and pictures of the fry.
A less expensive alternative to getting a discus pair is to purchase 12 or more of the same discus strain/color when they are young. The odds of getting a breeding pair are usually pretty good. Many Discusguy.com customers have obtained breeding pairs in this manner.
I hope this information is helpful.
Feel free to contact me if you have any additional questions.