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i've read in books that about a week old you can tell the gender of the fry if cut blackcardboard to go on the back of a 2 gal. tank and cut a 1/2 in. hole in the middle, the fry will go through the beam of light and you can see the gravid spot with a magnafieng glass and the ones who don't have it are males.
can i see a pic. of what5 that gravid spot on a week old fry will look like for females and males?

This from a guppy breeding site...

"Guppies can be sexed from about 4-5 weeks. The males have a modified anal fin, this is called the gonopodium"

What books are you referring to ?

I'd think sexing the fry at one week would be next to impossible.

The Amazon Nut...

Here's another article to help you in your Guppy breeding quest.... Unrelated to this but thought you'd find it interesting..

From the International Fancy Guppy Association.

http://www.ifga.org/articles/1articles.htm

Last edited by DaFishMan at 30-Oct-2005 08:35

The Amazon Nut...

See the gravid spot in newborn fry? I thought the gravid spot was really only visible when a fem was pregnant. I always look at the bottom fins to determine my guppies sex and never the gravid. Unless I can cleary tell one is pregnant in the tank at the store.

Last edited by ladiejl at 30-Oct-2005 16:49

i read it in a step by step book about guppies.null

While I find it hard to believe that you can see the gravid spot at one week old (and I get a headache just thinking about trying to see it through a magnifying glass of fry that are SO small and fast!) I suppose it could be true. On the other hand, I've seen fry turn into males when I was almost sure they were a female!

As for the gravid spot, ladiejl, it depends on the fish. Most of my guppy girls are light colored, so the gravid spot is ALWAYS visible. The one girl that I have that it is hard to see the gravid spot on is the half-black girl (silvery front, blue/black from midpoint through the tail).

In general, fry seem to develop and look like females until they are a few weeks old, then the males start forming gonopodiums. If you watch your fish closely, you can identify the gonopodium before the fish understands how to use it. I don't allow free-for-all breeding in my tanks, so as soon as I can identify males, they are separated. I currently have four young males in a net breeder until they are old enough to be put in the male tank, or I setup a bigger temporary home for them.

~Meow. Thus spoke the cat.~

The gonopodium, found on male livebearers, is a modified anal fin that extends from its stomache and looks kind of like a tail. If you cant tell, put it with the males.