If a fish in your tank dies, to be sure you want to determine the cause of death. Critters don't normally die for no reason at all, with the exception of maybe old age. Some of the causes that can contribute to illness include bacterial diseases, parasites, and poor water quality. It is important before introducing new occupants into the aquarium that the cause of an illness has been eliminated. Otherwise, the underlying cause may be carried over to new introductions, and in all likelihood they will share the same fate as the first.
If a sick fish isn't quite dead and you have exhausted all possible treatments to save it with no results, you may want to consider euthanasia to put it out of its misery. Whether you help a beloved fish friend make its final transition or it passes on its own, there are a number of choices as to how to dispose of it. Here are some methods that can be used. A few are rather abrupt, but most are caring and creative. A ceremonial prayer or burial service can also be included for added comfort and closure, particularly if you have children.
- Flush it down the toilet.
- Flush it down the toilet, but perform a ceremonial "Burial at Sea".
- Run it through the garbage disposal.
- Seal it in a plastic bag, then place it in the freezer and save it.
- Seal it in a plastic bag and deposit in the garbage.
- Seal it in a plastic bag or a box (plain or decorated) and bury it in the yard. A grave marker is optional.
- Immortalize it in a "Special Flower Pot Memorial".
- Perform a Viking funeral.
- Cremation.

