Freshwater Forum: Euthanizing Fish

Learn how to euthanize and spawn fish.

Q. I had a goldfish that got dropsy, which I diagnosed by comparing its symptoms to those described in a couple of goldfish books I have.

My fish resembled a pine cone and just sat on the bottom of the aquarium. The outlook in the books was grim and my fish eventually died.

I put the sick fish in a separate quarantine aquarium, because I have two other fantail goldfish that are (thank goodness) still alive and healthy. I’ve stepped up water changes and general water care so this doesn’t happen again.

Anyway, in my books, it mentioned that “humane euthanization” was best if a fish contracted dropsy, but it didn’t say how to “humanely euthanize” a fish. If this should happen again, what are your suggestions?

I also have a question about Plecostomus cats. I don’t currently have any, and I don’t think they would do well in my little goldfish aquarium. Is all algae good for plecos to eat?
Karen Mehren
San Diego, California

A. I’m sorry to hear about your goldfish. You have several options when euthanizing a fish:

• With your fish in a net placed on a hard surface, give it a quick blow to the head using a blunt object, such as a wooden dowel, broom handle, etc.

• Place your fish in a plastic bag containing water, seal the bag and place it in the freezer. As the water cools down and eventually freezes, the fish gradually goes to “sleep.”

• Place your fish in a bowl of water and drop in an Alka Seltzer tablet. The tablet gives off carbon dioxide and therefore decreases the partial pressure of oxygen, and the fish will gradually succumb.

• If you are not able to perform these tasks, ask your veterinarian to euthanize it for you.

No, plecos won’t eat all kinds of algae. In addition to any algae that may exist in a tank, supply plecos with sinking algae wafers, pieces of zucchini squash weighted to the bottom (remove the zucchini at the end of the day) and make sure there’s a piece of driftwood in the tank. There is some evidence that driftwood is important in the diet of plecos. Maintain excellent water quality as many species of plecos are sensitive to sudden changes in water conditions and to the build up of nitrogenous wastes.

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Fish · Lifestyle