Instructions
Wait for the baby guppies to reach adult size before selling. This usually takes about three months. If the water temperature in the tank is too cold it will take longer. Guppies prefer a water temperature around 75 degrees.
Check local regulations to make sure you don't need a business license to sell your guppies. Typically, a fish hobbyist will not need a license. However, a large-scale guppy breeding operation could require a business or breeder license and some states require a license of anyone selling to retail establishments.
Contact pet stores in your area to see if they might be interested in your overage. Large chain pet stores usually only deal with large commercial fisheries. It is common for pet stores that will take your guppies to exchange your fish for store credit.
Place classified ads in the local newspaper and online services. Guppy forums often offer classifieds that effectively reach your target market.
Price your fish to move them. Guppies usually sell in pet stores for about $3. You can usually expect to sell private party for about one-half of retail price.
Sell your guppies locally. Fish do not travel well; if you attempt to ship guppies many will die in transit.
How to Sell Guppies
Guppies are prolific breeders, bearing live young called fry. It is common for guppy owners to find themselves with an over-populated tank. Guppies are a popular fish and relatively easy to sell. However, don't expect to make a lot of money. Guppies are a relatively inexpensive fish to purchase at retail and a private seller can expect to sell for significantly less. Options available to the amateur fish keeper trying to sell excess guppies, are private party sales or attempting to sell to a retail pet shop.