Formalin and fish

[Spare time]

I was curious, does anyone know if the treatment of fish with formalin or a formalin based product may decrease their lifespan? This is assuming they don't have a deadly disease that needs the treatment? @Jay Hemdal Ever noticed anything with fish long term after treatment?

 

[Jay Hemdal]

I was curious, does anyone know if the treatment of fish with formalin or a formalin based product may decrease their lifespan? This is assuming they don't have a deadly disease that needs the treatment? @Jay Hemdal Ever noticed anything with fish long term after treatment?

This topic keeps coming up. There are a couple of people here who are adamant that formalin (and sometimes copper) is a "death sentence" and fish treated with it will die an early death, usually after two years or so. This is not borne out in my 50+ years of using it. There are also NO indications of this in any of my dozens of fish disease books and papers. These people were so adamant though, that I recently posed this question to a public aquarium list serve - and nobody there had seen this issue either.

Formalin can be an acute poison, but there is no long term mortality associated with its use.

I relegated this issue to my "aquarium myths" article:

Myths and Misinformation - fish edition

These are often repeated bits of information that are perpetuated by people using old or incorrect information. Once it becomes "common knowledge" it continues to spread through the Internet, often being changed or over-simplified in the process. These are some examples of misinformation about...

www.reef2reef.com

That said, formalin is very toxic to use in a home. It de-gasses from the water into the air and that is just not acceptable in a home situation. If you must use it, you must have proper PPE, and I would try to vent the room air outdoors if possible. Formalin that is stale or has been stored improperly (frozen) can produce a white solid in the container. This paraformaldehyde is extremely toxic to fish (but again, it is acutely toxic, it doesn't up and kill fish two or three years later). Methanol is used as a preservative for formalin. Levels higher than 15% should be avoided.

Here is a good aquaculture data sheet on it:

https://fisheries.tamu.edu/files/2013/09/Use-of-Formalin-to-Control-Fish-Parasites.pdf

Note - it is actually FDA approved for use in food fishes now.

Jay

 

[Readywriter]

I was curious, does anyone know if the treatment of fish with formalin or a formalin based product may decrease their lifespan? This is assuming they don't have a deadly disease that needs the treatment? @Jay Hemdal Ever noticed anything with fish long term after treatment?

Either way they will be well preserved

 

[fish farmer]

I was curious, does anyone know if the treatment of fish with formalin or a formalin based product may decrease their lifespan? This is assuming they don't have a deadly disease that needs the treatment? @Jay Hemdal Ever noticed anything with fish long term after treatment?

First I've ever heard of this. I've been using formalin on salmonids for 30 years. I routinely use it on trout eggs for fungus management. Some of my trout brood stock live up to 10 years before I dispose of them. Feral fish that have been treated and released in the wild may live longer than that.

Perhaps certain sensitive species have issues with it. I work with certain wild rainbows that has sensitivity to exposure to other common fish culture chemicals such as Chloramine T.

I even know I guy who chugged a shot of formalin thinking it was alcohol. Immediately hit the floor, but survived and got a plastic stomach out of the ordeal, still alive and hasn't gotten cancer from it, happened about 30 years ago.

 

[Spare time]

This topic keeps coming up. There are a couple of people here who are adamant that formalin (and sometimes copper) is a "death sentence" and fish treated with it will die an early death, usually after two years or so. This is not borne out in my 50+ years of using it. There are also NO indications of this in any of my dozens of fish disease books and papers. These people were so adamant though, that I recently posed this question to a public aquarium list serve - and nobody there had seen this issue either.

Formalin can be an acute poison, but there is no long term mortality associated with its use.

I relegated this issue to my "aquarium myths" article:

Myths and Misinformation - fish edition

These are often repeated bits of information that are perpetuated by people using old or incorrect information. Once it becomes "common knowledge" it continues to spread through the Internet, often being changed or over-simplified in the process. These are some examples of misinformation about...

www.reef2reef.com

That said, formalin is very toxic to use in a home. It de-gasses from the water into the air and that is just not acceptable in a home situation. If you must use it, you must have proper PPE, and I would try to vent the room air outdoors if possible. Formalin that is stale or has been stored improperly (frozen) can produce a white solid in the container. This paraformaldehyde is extremely toxic to fish (but again, it is acutely toxic, it doesn't up and kill fish two or three years later). Methanol is used as a preservative for formalin. Levels higher than 15% should be avoided.

Here is a good aquaculture data sheet on it:

https://fisheries.tamu.edu/files/2013/09/Use-of-Formalin-to-Control-Fish-Parasites.pdf

Note - it is actually FDA approved for use in food fishes now.

Jay

Thank you for your response!