[header] How to acclimate a fish [title] Turn off aquarium light and dim the lights in the room where you're aquarium is set up. [step] Do this before you remove your fish from the carrying container, since fish are sensitive to light and may be traumatized by a sudden change in lighting. [substeps] Once your fish is used to the tank, you can be less strict about lighting. 
It's a good idea to initially introduce your fish to a dim environment, as this will reduce the shock of being introduced to a new environment. [title] Float the bag in the water for 15 minutes.