Long Term Effects of Formalin in Ornamental Fish?

Question

Sadly a mild outbreak of costia has recently ravaged my poor opaline gourami. Sad as it is, it is just a fact that its here, and has to be dealt with. The gourami was housed with 2 adult, breeding Jack Dempseys, who neither appear to be afflicted with the flagellates. Understanding the nature of this infection I immediately quarentined my gourami in a small 10 gallon hospital tank, and I've increased the salinity of my water from .03 to .06% last night.

The gourami appears to respond well to the treatment, however it obviously will not clear in a day. Further, the Dempseys appear to still be unaffected today, however my concern comes from the idea I may be put in a position to administer formalin into my water.

As the fish will obviously intake some of this substance through natural processing of the water, along with osmosis, should I have many concerns for the long term well being of my fish under the treatment of an aldehyde solution? Should I keep an eye out for any specifics?

Added: I've been looking into this most of the day, I'm glad to know that since I've already increased the salt this may effect the medication. I have also been reading that potassium pomegranate is a good alternative for someone like me who may be worried about things like formaldehyde in my water. Have you ever used this?

Answer 1

Thanks for the recommendation, Poopy!

I have used formalin (as an ingredient in the most effective ich cures along with malachite green). The is the possibility of long term effects, not only to the fish, but to you if you come into contact with the formalin in concentrated doses or for extended exposure of smaller doses - it's a known carcinogen.

While this doesn't guarantee that it will cause cancer, it does increase the risk for developing it.

It also reacts with dissolved oxygen, so if your tank is at a higher temperature, or you have poor water circulation, this could be another potential cause for concern.

Rather than present this as my opinion, here are three sources backing up this information:
hazardous materials data sheet for formalin (you may want to skip down to the "Heath Hazard Data" section)
- http://www.aq-products.com/AP%20MSDS%20Sheets/FORMALIN%20FM-1%20ISSUE%201.pdf -

from an aquarium websites -
http://www.wetwebmedia.com/formalinart.htm
http://www.skepticalaquarist.com/docs/health/formalin.shtml

NOTE: Although both formalin and malachite green are carcinogenic, these are the medications of choice for costia. It may help quicken your treatment if your fish are able to withstand an elevation in temperature. If you can raise it to 86-90o, the parasite itself doesn't tolerate these temperatures well. Just remember that as the temperature increases, the amount of dissolved oxygen in the water decreases, and since the formalin can decrease it further, keep a close eye on your fish, and maintain/increase water circulation to help them out.

Answer 2

I'm not sure how much different gouramis and Jack Dempseys are from koi, but I can tell you I use Pro-Form C (main ingredient = formalin) with them all the time, with no observable ill effects.

Since the pond my koi are in is outdoors and is open to all kinds of wildlife, etc., visiting, I have my fair share of "critter invasions" from time to time. Pro-Form C and Praziquantel are always my meds of choice as the Pro-Form can get just about everything but flukes, and the Prazi works on flukes wonderfully well.

The only thing I would tell you to watch out for is a) dose *precisely* - follow all measurements and number of doses, etc., to the "T", and b) check the label of your formalin product carefully, as there are some that cannot be administered unless the water is within certain parameters with regard to temperature and salinity. I made the mistake of using a particular product one time when I had already put salt in my water, without checking the label, and the combination ended up stressing the fish very badly as I think I burned their gills.

For indoor tropical fish, ideally you would get a Magic Man, Copperhead, JonV, SoupNazi, etc., answer as I'm sure they know more about how formalin products affect the species you're working with, in particular.

Anyway, hope this helps. Good luck!

Answer 3

Formalin is a generic term which describes a solution of 37% formaldehyde gas dissolved in water. Solutions of formalin for use on fish should contain 10 to 15% methanol, which inhibits formation of paraformaldehyde a toxic compound but not lethal in small dosage.

Formalin is used as a bath treatment to control external parasitic infections of fish. It is extremely effective against most protozoans, as well as some of the larger parasites such as monogenetic trematodes. Formalin effectively kills parasites on gills, skin, and fins. It is not the preferred treatment for external bacterial or fungal infections.

There is no long term effect of Formalin in fishes, as long as you change 50% water after the treatment is complete and the infection is contained.