Acclimating Your Betta
When you get your betta in the mail, you should carefully take the bag out, but in low light. Bright light might freak the fish out and it could go into shock. Your going to need to float the fish in its need tank for a few hours. The fish must have been use to a different water temp thoughtout shipping. Again floating will allow the temperature to equalize and avoid shock.
After a few hours, cut open the top of the bag and slowly pour some of the tank water into the bag. Doing this process for a few hours will again be best for the betta. After the betta is doing good and breathing normally, then turn off the lights and aloow the betta to swim out on its own. Leave the lights off, and if there are fishes in the tank already, feed them.
What seperates acclimating shipped fishes over petstore fish, is the amount of time. Your going to need to give the shipped fishes alot more time than petstore shipped fishes.