Thermal Shock & Chlorine Poisoning

humpingtheheater150, originally uploaded by rkbentley.

Q: KM wrote,

When doing a total water change for our male betta, "Patches", my 6 year old daughter thought she was helping, and decided to fill the aquarium with tap water and to ahead a put the fish in when I stepped away to take care of another matter. He seemed fine last night, but this morning he is listless, and staying at the top while slowing taking in air. Is there anything that can be done to save him??

A: There are a couple of things that could be troubling to your betta in this case. First is thermal shock. Fish, as you know, are sensitive to rapid fluctuations in water parameters with temperature being one of the most significant. To avoid shock we try to keep the temperature variable down to about 2 degrees Fahrenheit or 1 degree Celsius per 24 hours with an ideal temperature of about 78F [25.5C]. I have no idea what the temperature difference was between the old water and the new aquarium water but it would be a small miracle if your 6 year old was able to keep it even remotely close to same temperature as the old water. The best thing you can do is to bring the water into a survivable range (if it is at some extreme) and then slowly over hours or even days bring it back to the ideal.

The second problem is chlorine/chloramine poisoning. Most of us have tap water that is treated with chlorine and/or chloramines to prevent pathogens from infecting us. While it's safe for us to drink it can be deadly to our fish. It sounds like you are already treating the water in your regular routine so in this case the best thing you can do is add your regular water conditioner to the tank as soon as possible to avoid further toxicity. If your Betta appears to be struggling to breathe, which can sometimes happen when exposed to poisons like chlorine, ammonia, etc; you may find adding an air stone to tank can ease the burden somewhat. He will continue to use his labyrinth organ to get atmospheric oxygen but may be able to retrieve more dissolved oxygen from the water if there is an air stone to supplement.


Unfortunately, this is just a tragic accident and there isn't any quick fix to save your betta. All you can do is get the betta into livable water as soon as possible and then work to slowly bring it back to it's ideal range. If your betta survives then the next step would be to prevent future incidents, which I bet you're already on top of. Also, continue to monitor him daily for signs of disease. Sometimes bettas are able to survive traumatic events but will later come down with diseases as a result of a weakened immune system.

All the best to you, your daughter and Patches.