A pet goldfish can be expected to live 10 years or longer if it is properly cared for. Some goldfish have been documented as living for more than 20 years with the oldest known specimen dying at the age of 43, according to Tropical Fish Data. Regardless of the length of the fish's lifespan, all goldfish will die at some point in time. It is important to dispose of the remains properly, especially if the death was due to sickness or disease.
Put on gloves and remove the dead fish from the tank using the fish net as soon as you have ascertained that the fish is in fact dead. Dead fish should never be left in a tank that has other fish in it due to the risk of spreading disease or the decomposing matter contaminating the tank.
Determine if the fish is small enough to be disposed of by flushing it down your toilet. Flushing fish is a safe and effective way of getting rid of the remains, but only if the fish is small enough to fit through your plumbing system, meaning it is less than 3 inches long. If the goldfish is small enough to be flushed down the toilet, you should do so. Do not touch the fish with your bare hands.
Dispose of fish by placing it in the garbage with other waste. Before putting it in the trash, place the goldfish in a small plastic bag and seal it tightly, pressing all the air out as you seal it.
Goldfish that are killed by disease may make the other fish ill, so it is important to remove the dead fish as soon as possible. You may also want to change the water in the tank immediately after finding a fish dead. Some people may wish to bury their dead goldfish in the plastic bag rather than throwing it away. This is optional.
Do not touch dead fish, as they may have bacteria on their bodies that could be harmful to you or other fish you come in contact with after touching the dead fish.