How long does it usually take to tell what gender the fry are? I have like 12 fry in my current tank and I want to sell them but I have no clue what gender they are.
Depending on growth, on average, I'd say 2 to 4 months to determine gender.
Chains typically won't deal with hobbyists as they have a supply chain dictated by corporate and a rule of thumb for many/most mom & pop fish stores is to pay 1/3 of the retail selling price for fish. This can often translate to $1 per fish. If your Guppies are very colorful 'fancy' you could get more and prices are almost always higher in more urban areas.
EDIT: Oh and unless you have a huge breeding operation selling hundreds of fish you'll be fortunate to cover the cost of fish food and supplies...been there, doing that!
