how long before putting fish in tank
First, you need to cycle the tank before adding fish. If you just fill it up with water, and put them in, they will die. Cycling takes anywhere from 2 weeks to over a month. Once you've cycled your tank and are ready to add the fish, don't just bring them home and throw them in. They should come in bags. Sit those bags with the fish in them in the tank water for about 30 minutes so they slowly get used to the new temperature. Then it will be safe to put them in.