I brought a new fish tank and put tap water in the tankall my fish are at the bottom just lying there Can you leave the tank water as it is and wait till next time to change it or will the fish die?

Your tap water may be chlorinated. Chlorine is a poison to kill germs, used in tap water and Swimming Pools. It gives the water a blue tint. It will also kill your fish. It will even kill people if the dose is high enough, and it was used as a poison gas in World War 1. If such is the case, you have poisoned your fish. Water without chlorine should be used, spring water or distilled water. If you must use tap water, you can buy conditioner to make sure the balance of chlorine so that it will not kill you fish from good pet shops such as Pets at Home Hope this helps

that is true but another reason for that could be that the oxygen levels are low (water my not be circulating enough if at all) in which case the lower down they are, the more oxygen there is. they might also swim up to the surface and get breaths from there.