Sodium Thiosulfate

[Humblefish]

I would like to learn more about using sodium thiosulfate to neutralize bleach.

For example, let's say I wanted to dose 100ppm chlorine into a 40 gal QT for disinfection of Cryptocaryon and other microbes. According to this chart, I would need to use (roughly) 1 Cup of 8.25% sodium hypochlorite: http://dec.vermont.gov/sites/dec/files/dwgwp/DW/chlorinedosageemergencydisinfection.pdf

In 24 hours I am ready to remove all chlorine from the tank, so according to this information provided by @bblumberg I would use about 34 grams of sodium thiosulfate for 40 gal/150L of water @ 100ppm chlorine: https://www.edspumps.com/water-treatment/documents/Antichlorination.pdf

Now, if my math is right (34 grams/40 gals = 850mg/gal = 224.5mg/L or ppm), then I am exceeding the 100ppm limit of sodium thiosulfate which can be safely used with fish. Or does most of the sodium thiosulfate dissipate soon after dosing or get used up when neutralizing chlorine? What about the remaining Thiosulfate after the Sodium is bonded to the Chlorine from the bleach?

@Randy Holmes-Farley @Christoph

 

[Christoph]

Hi!

The imperial system is complicating this for me big time .

Is it right, that 1 cup is ~235 ml?

If thats the case, this would be around 19.4 g sodium hypochlorite, you would need about 20.6 g (anhydrous) sodium thiosulphate to nuetralize this amount of bleach. The thiosulfate is consumed in the neutralisation reaction giving you sodium chloride and potassium hydrogen sulfate (which is lowering you alkalinity, so its best to measure & dose if necessary before adding fish). Also i would recommend getting a chlorine test kit, to check if neutralization of the bleach was successful.

Best,
Christoph

 

[Humblefish]

Hi!

The imperial system is complicating this for me big time .

Is it right, that 1 cup is ~235 ml?

If thats the case, this would be around 19.4 g sodium hypochlorite, you would need about 20.6 g (anhydrous) sodium thiosulphate to nuetralize this amount of bleach. The thiosulfate is consumed in the neutralisation reaction giving you sodium chloride and potassium hydrogen sulfate (which is lowering you alkalinity, so its best to measure & dose if necessary before adding fish). Also i would recommend getting a chlorine test kit, to check if neutralization of the bleach was successful.

Best,
Christoph

Thank you, sir!

 

[Cory]

By the way, iirc bleach is neutralized by hydrogen peroxide. You might want to use that instead.

 

[Christoph]

Cory, you might end up with leftover H2O2 that could be a problem by itself.

Best,
Christoph

 

[Cory]

Cory, you might end up with leftover H2O2 that could be a problem by itself.

Best,
Christoph

I agree it may not be the safest way but can work.

 

[Humblefish]

By the way, iirc bleach is neutralized by hydrogen peroxide. You might want to use that instead.

I agree it may not be the safest way but can work.

I looked into the possibility of using H2O2, but concluded sodium thiosulfate would be the safer option.

 

[bblumberg]

I would like to learn more about using sodium thiosulfate to neutralize bleach.

For example, let's say I wanted to dose 100ppm chlorine into a 40 gal QT for disinfection of Cryptocaryon and other microbes. According to this chart, I would need to use (roughly) 1 Cup of 8.25% sodium hypochlorite: http://dec.vermont.gov/sites/dec/files/dwgwp/DW/chlorinedosageemergencydisinfection.pdf

In 24 hours I am ready to remove all chlorine from the tank, so according to this information provided by @bblumberg I would use about 34 grams of sodium thiosulfate for 40 gal/150L of water @ 100ppm chlorine: https://www.edspumps.com/water-treatment/documents/Antichlorination.pdf

Now, if my math is right (34 grams/40 gals = 850mg/gal = 224.5mg/L or ppm), then I am exceeding the 100ppm limit of sodium thiosulfate which can be safely used with fish. Or does most of the sodium thiosulfate dissipate soon after dosing or get used up when neutralizing chlorine? What about the remaining Thiosulfate after the Sodium is bonded to the Chlorine from the bleach?

@Randy Holmes-Farley @Christoph

As far as I understand, sodium thiosulfate is consumed in the reaction with sodium hypochlorite (bleach), being transformed to sodium sulfate according to the equation below.

4 NaClO + Na2S2O3 + 2 NaOH → 4 NaCl + 2 Na2SO4 + H2O

I made a calculator (attached) based on the link you noted above that accommodates various scenarios one might encounter using bleach to disinfect aquariums, etc.

 

[Humblefish]

Thank you @bblumberg!!!

 

[bblumberg]

Happy to help.

 

[Victoria M]

I was thinking about this kind of thing for my QT system. I thought it had less risk of contamination and easier than what I was doing. I scraped the idea ultimately because it is one tank, unlike your situation @Humblefish. But I do like the idea of decreasing the risk of contaminating my fishroom. So I think I am going to add bleach to the QT water prior to emptying the tank for a reset. My QT is rather obnoxious and full of potential parasite hiding places and messy things to fling contaminated water drops around the room.

 

[DrZoidburg]

It gets oxidized by the bleach to sulfate. Even if you had an excess of thiolsulfate, it is really easily oxidized by the environment. Vitamin C will also make the bleach safe.