Once you have picked out your tank, location and the type of fish you wish to keep, you will most likely be chomping at the bit to get fish in your tank as quickly as possible. Try to be patient and remember that your water needs to be just right for the health of your fish. The first step is to add a water conditioner which will de-chlorinate your tap water. Chlorine is very dangerous for fish and can cause necrosis (cell death) in their gills, leading to suffocation. Never add unconditioned water to your aquarium.