It is arguable that fish feel pain in a similar manner to humans but it is with out doubt that a fish that cannot control its swimming behaviour or is unable to function normally is suffering in some way and will not live a comfortable and full natural life. Similarly, despite our best efforts, some fish become too sick to treat effectively or may be carrying a disease such that it poses a serious health risk to the overall aquarium. In these cases, one needs to be cruel to be kind and euthanasia should be considered.

I must stress that the decision to destroy a fish should not be taken lightly. Even badly wounded fish often recover and some infections often look worse than they are.

Veterinary surgeons use a chemical called MS-222 to induce an irrecoverable deep sleep however, this chemical is a controlled substance and professional euthanasia is often an expense that few aquarists can afford. There are however, alternative methods open to the aquarist.

The best methods are short and sharp techniques. These may seem barbaric but I assure you I have the fishes interest at heart.

The first option is to remove the fish and firmly grip it by the tail with the aid of a paper towel to prevent slipping and knock the fishes head firmly on a solid surface. Provided the blow is sufficiently hard, death is instantaneous. Many people however, cannot bring themselves to commit this act and the aftermath can be messy.

An alternative is pithing. This is where a sharp knife is run through the fishes brain or the spinal chord is severed between the body and the head. Pithing is relatively straight forward with small fish but in larger specimens it if often difficult to perform a quick, clean cut due to the thickness of the skull and the probability that the fish will be squirming about. Again this method is potentially messy and not the easiest act to commit.

My preferred method is to freeze the fish. The fish can be removed from the aquarium, transferred to a bag or plastic container and placed in the freezer. The fish need not be frozen but left for one or two minutes to die from thermal shock. It is not the quickest method but perhaps the easiest to perform emotionally.

Methods to avoid are flushing the fish down the toilet (difficult with large fish anyway), as death does not occur quickly. Certainly with cooler water species, the temperature change is not enough to induce thermal shock. Instead the fish is stressed by an unfamiliar environment which may not kill it outright. Asphyxiation, by removing the fish from the aquarium, should also be avoided as some fish can survive extra ordinary lengths of time simply by remaining moist.

Inevitably you and your fish must part at some point. A natural death is easier to cope with but, by understanding the practical points of euthanasia, it will make the emotional ordeal of losing a treasured fish much easier to accept.