How long do you let fish water sit out?

at least 24 hour then float it for 15 min. put a cup of aquarium water in it the net the fish in . DON'T PUT HE STORE WATER IN YOU AQUARIUM!!!!!!!!!!!

Edit: It depends on what size aquarium it is if it is less then five gallons then you should take the fish out when cleaning if it is anything bigger then that then you should only be taking 25% percent of the water out at once which means you wouldn't have to wait to put your fish in because you don't take them out. If your asking how long you should wait to get fish after starting up an aquarium its at least a day but its better to wait a couple days. And if your putting the fish into your aquarium then you want to float the fish in a bag of water for 10-15 minutes before putting them in.