Considering that you just started posting questions about sand and building a sump 10 days ago, you're not cycled. You should go to the "getting started" forum group and read the sticky note threads.
Cycling the tank creates bacteria that consume the poisonous ammonia that fish poop (basically). Without cycling your tank any fish added will likely die. Adding more than 1 will increase the chance of death.
Acclimating a fish involves slowly adding tank water to the stores water in the bag so the fish aren't shocked to death when they get dumped into the tank.