It sounds like you are new at this. You need to de-chlorinate the water before you put your fish into it. You can leave an amount of water equal to the fish tank out for 24-48 hours. The chlorine should dissipate. If you don't do this, it's like throwing the fish into a bath of poison. Chlorine is a toxic chemical. You also need to buy a little bottle of a chemical mix that I can not think of the name of at the moment. Ask at the pet store or pet department. It reduces the chlorine, puts something in the water to stop the "Ick" which is what might be on the fish's tail, and adds other chemicals to the water that makes your fish live. Good luck with all of this.
