How to Tell the Sex of a Guppy

You can identify the sex of a guppy by examining its fins.

Among the many types of fish who have captured the hearts of aquarists, guppies play a prominent role. These minute, yet cute fish have the ability to add a sense of liveliness and color to any aquarium or fish tank. Identifying the gender of guppies is important, especially if you want to them to breed. Though it may seem an impossible task to identify the gender of such small fish, in fact it is quite easy, but requires careful observation.

Things You'll Need

• Small fish tank
• Magnifying glass
• Fish net
• Small lamp

Instructions

1. An aquarium crowded with fish does not allow for good observation. Therefore, use the net to capture the guppy. Immediately transfer the guppy to a small fish tank for easier identification.

2. Shine the lamp onto the small tank. This should make it easier for you to identify the colors of the guppy.

3. If needed, hold the magnifying glass close to the fish tank, to magnify the guppy. Check the size of the guppy. If the guppy has a swollen abdomen and has a black spot on the rear part of the abdomen, then it is definitely a pregnant female.

4. It is a little harder to identify the gender of a non-pregnant guppy. Use the color for identification in this case. The particular color of the guppy is irrelevant, but its shade is important. Closely observe the brightness of the color of the guppy.

5. Males usually have brightly colored bodies while female have less brightly colored bodies. Scientific research has shown that females always prefer males who have brightly colored bodies.

6. To confirm the gender of the guppy, look at its body. Male guppies usually have slimmer bodies than females.

7. You can also identify the gender of a guppy by looking for its gonopodium, a type of modified fin. A male has a gonopodium, while a female does not possess one.

8. After identifying the gender of the guppy, carefully catch the guppy in the fish net and place it back in the aquarium. Be extra careful with pregnant guppies. You may have to keep the pregnant guppy separate since most fish eat newborn guppies.

References

• The Center for Connected Learning (CCL) and Computer-Based Modeling; Guppy Spots; Uri Wilensky; 2006
• Sex, Color and Mate Choice in Guppies; Anne E. Houde