Sodium Thiosulphate

[MikeM]

Questions about this inexpensive dechlorinator:

1. Once placed in a pond, how long before ST degrades and is no longer effective to neutralize chlorine?

2. What does it react with other than chlorine?

3. When crystals are mixed with water to form a solution, how stable is it ? In other words, what is the shelf-life (assuming nothing added as a stabilizer).

4. Is there any negative to using it as a dechlorinator? (I've never heard of any, but doesn't everything have some side effect?)

Any chemists in the house?

[Arthur]

Questions about this inexpensive dechlorinator:

1. Once placed in a pond, how long before ST degrades and is no longer effective to neutralize chlorine?
>>> 48 hours, less is very sunny conditions

2. What does it react with other than chlorine?
>>> any oxydant in the water (e.g., PP)

3. When crystals are mixed with water to form a solution, how stable is it ? In other words, what is the shelf-life (assuming nothing added as a stabilizer).
>>> not much, a few days, maybe a week

4. Is there any negative to using it as a dechlorinator? (I've never heard of any, but doesn't everything have some side effect?)
>>> none as long as you understand that it does not neutralize ammonia or chloramines and that no PP treatment will have effect within 48 hours.

[dick benbow]

Whew, Thanks Arthur! That's some good helpful info. ( ain't it great being able to draw from such a good knowledge pool! )

[Arthur]

Well Dick thank you. You know I try to help as much as I can but I am very busy so sometimes answers come delayed. This time I was lucky as I saw MikeM's questions 2 hours after he posted :-)

News from Japan: our koi shipment is coming in next week (no exact date yet). The issues are 1) there is still about 8' of snow in the Niigata mountains, and 2) many breeders shared ponds in order to save koi last October, now they have to go through them, identify, count, etc.

I will keep you posted.

[bekko]

For shrimp hatchery use, seawater is chlorinated and dechlorinated before use. In that application, it is important to not overdose the ST as using more than is needed to neutralize the chlorine has a toxic effect on shrimp larvae and the single cell algae used to feed them. Thus, I would worry that excess ST could impact the pond biota - but probably not the koi themselves.

Use 6.7 mg/L (about one ounce per 1000 gallons) sodium thiosulfate to reduce 1.0 mg/L (ppm) chlorine.

-steve hopkins

[MikeM]

Arthur: Thank you!

Follow-up: ST products sold in liquid form are often on store shelves for a long time. What is used to stabilize? (I see nothing noted on ingredient labels I've bothered to check.)

Steve: Nice info. I've always heard that an "overdose" of ST had to be many, many times the amount needed to neutralize chlorine before any risk to fish. But potential harm to the total biomass is new to me.

[Arthur]

Follow-up: ST products sold in liquid form are often on store shelves for a long time. What is used to stabilize? (I see nothing noted on ingredient labels I've bothered to check.)
>>> I read a report about this some time ago, a quick search did not find it.
>>> Will reseach more tonight.

Steve: Nice info. I've always heard that an "overdose" of ST had to be many, many times the amount needed to neutralize chlorine before any risk to fish. But potential harm to the total biomass is new to me.
>>> I would not use an overdose of ST because, once the chlorine is gone,
>>> it will reduce the oxygen in the water. Always vigorously aerate the pond
>>> water when using ST.