how long until the sex is determined?

I have pretty much all the livebearers there are and I was wondering how long until the sex of the fry's are obvious? I have a bunch of new guppies and I want to get rid of them, but I want to make sure I know what sex they are before I do. Any help is appreciated. Thanks

 

I think you can tell by 3 months, but i'm not sure.. it varies I think with livebearers depending on how they grow, etc.. can you tell a difference in the amount of color in the fry? I think with the gups you can use coloring as the first sign of male/female.

 

HI Fishyfarm. Good luck getting rid of them. Our fish stores aren't exactly acting interested. One accepted them... for free. The other one wants batches of at least 100 mollies (we have mollies)!

I am starting to tell the sex and they're 2 months old.

 

I think my gups are about that old. so far they all look female. No color what so ever to them.
I asked my pet store and they don't want them so i'm trying to give them away free on craigslist. I can't keep them because I already have enough fish in my tank as it is.

 

Actually, I was wrong. I thought I could tell the sex, but basically they were pretty much all females too. Then I was in another thread about this and this guy says that he can tell from a few weeks old, but that most people can tell after about 3 months or so, and that by then, they'll stop all looking like females.

 

Must depend on area and stocks of fish store. The Jack's Aquarium in my area (Beavercreek, Ohio) said they will take my baby platies when they grow. They offered 33% of the sale price for them and I have 69 so I asked if their was limit and they said "No bring in as many as you wish."