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  1. #1

    Shelf life of Sodium Thiosulphate solution

    Hi All

    I have dissolved 125g of ST into 1 litre of boiling water. How long will this soluion be safe to use as a dechlorinator? Weeks, Months?

    Many thanks



  2. #2
    If a solution of pure sodium thiosulphate is made with distilled water under sterile conditions and stored in a cool, dark place its shelf could be measured in years but koi keepers can't do that. Common bacterial contamination by sulphur eating bugs will reduce its effective life which is why I suggest using boiled, and still very hot, water to kill any bugs in the water or on the crystals themselves.

    If this is done and the bottle is kept tightly sealed between uses then, bearing in mind that the crystals are inexpensive, I would suggest making up enough to last for about a year and, as a precaution, discard any that hasn't been used after a year.

  3. #3

  4. #4
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    You could be lazy like some of us on here are (certainly that includes me!) and throw in the actual crystals instead.

    I only use it if I do a big water change and run a hose flat out through the dechlorinator unit because I usually trickle in using RO water. But when I do I just chuck a few crystals in the clean side of my drum filter and let it dissolve in there as I run the new water in.

    You don't have to worry about shelf life then. I am so lazy I often don't even bother to weight them and just put in a teaspoon full on the basis that's usually more than enough. If you were doing it like this regularly though I would weigh it out on some gram scales (digital jewellers type job easily bought on eBay for a fiver). Once you know how many pinches are needed per day it would be incredibly easy to do that way. Manky might thing this is a heinous sin though

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  6. #5
    Not in the least Lara,

    I spoil my shoal of Koi Water Quality students rotten so I've worked out a whole range of tables for them in the course module. This is the one that refers to using sodium thiosulphate as a dechlorinator. As you can see, I've worked out the quantities for how they can use it either as dry crystals or made up as a solution that they can just pour into the stream of water as they top up the pond.

    The accompanying text says that the correct amount to use is 2.75 grams per 1,000 litres but its toxicity is so low that I've rounded up the quantities into easy to measure amounts and that, even at these generous values, precise measurement isn't necessary. (Although 2.75 grams per 1,000 litres is the correct amount but adding any amount less than about 100 kg per 1,000 litres still won't kill koi)



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  8. #6
    Moderator Rank = Grand Champion Feline's Avatar
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    I don't think I'm far out then with my teaspoon full for a decent water change

  9. #7
    Thanks MS and Feline!

    I just wanted to know as I mixed up 1 litre as per Manky Sankes diagram above to then find I only need 20ml per change! Didn't want to waste the solution so its good to know I can use it for approximately a year.

    When I set up a trickle in/out like you guys have, I will have to remember to add ST crystals to the pond every few day. Is there a way of automating the De-chlorination process? Maybe a cylinder containing a large amount of ST which the tap water can trickily through...saving the need to add the ST regularly?

  10. #8
    I change around 150 Gallons per filter clean and then wait 6 months for the trickle through my EA dechlorinator to refill the pond. Now going the lazy route am I safe to simply add a teaspoon of ST to let’s say the return section of my Nexus and then then put the hose on full blast and have no chlorine issues? I’m happy to even dissolve a teaspoon full in hot water.

    If this is safe to do has anyone got a link to purchase ST?

    Thanks

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  12. #9
    Quote Originally Posted by DAVID VIVID View Post
    I change around 150 Gallons per filter clean and then wait 6 months for the trickle through my EA dechlorinator to refill the pond. Now going the lazy route am I safe to simply add a teaspoon of ST to letís say the return section of my Nexus and then then put the hose on full blast and have no chlorine issues? Iím happy to even dissolve a teaspoon full in hot water.

    If this is safe to do has anyone got a link to purchase ST?

    Thanks
    Yeah mate. Just put right amount in jug. Warm water. Then throw in the pond where your putting your hose for top up. Full blast. And remember to put the st in pond first.
    Just go on ebay to buy your st crystals . Mine i buy are in plastic container.

    Sent from my SM-G925F using Tapatalk
    Last edited by freddyboy; 12-04-2018 at 01:00 AM.

  13. #10
    No wonder I am going through crystals like a dose of salts. I stick a couple of handfuls in a jug of boiling water every time I do a water change
    And now I see I only need 12.5 grams per 1000 gallons!!!

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  15. #11
    Quote Originally Posted by -Craig- View Post
    No wonder I am going through crystals like a dose of salts. I stick a couple of handfuls in a jug of boiling water every time I do a water change
    And now I see I only need 12.5 grams per 1000 gallons!!!
    With my 4000 gallons i trickle about
    1 litre every 2 minutes. And put 1 tea spoon full every 3 days.
    Hope this helps

    Sent from my SM-G925F using Tapatalk

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  17. #12
    Extreme Koi Member Rank = Mature Champion john1's Avatar
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    https://www.ebay.co.uk/itm/Sodium-Th...QAAOxyNo9SoPgf

    There you go,a lot have their own methods me included.

    I use a plastic measuring jug like my wife has in the kitchen,before i change any water i fill the jug with pond water and put in i level T spoon of s/t give it a stir and leave,than dump my water by the time i need to top up the crystals are dissolved and pour it in the stream of tap water.
    At least i know it is fresh every time.
    John

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  19. #13
    Quote Originally Posted by freddyboy View Post
    With my 4000 gallons i trickle about
    1 litre every 2 minutes. And put 1 tea spoon full every 3 days.
    Hope this helps

    Sent from my SM-G925F using Tapatalk
    That is really helpful to know. Thank you.

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  21. #14
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    Quote Originally Posted by willshill View Post
    Thanks MS and Feline!

    I just wanted to know as I mixed up 1 litre as per Manky Sankes diagram above to then find I only need 20ml per change! Didn't want to waste the solution so its good to know I can use it for approximately a year.

    When I set up a trickle in/out like you guys have, I will have to remember to add ST crystals to the pond every few day. Is there a way of automating the De-chlorination process? Maybe a cylinder containing a large amount of ST which the tap water can trickily through...saving the need to add the ST regularly?
    You could set it up in a container using a peristaltic dosing pump if you really wanted to. Or even do the cheapo way and use Hozelock irrigation drippers from a reservoir- but it would be quite hard to get the flow rate exactly right.

  22. #15
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    Hi All,

    Question, I intend to have a trickle feed running into my Nexus 220 as per below video:

    https://www.youtube.com/watch?v=rp0UNEnZHuE

    If i was to position the trickle inside the nexus near to where the water is sucked out of nexus by pump exit would this effect my bio area of nexus?, don't want to undo any bio build up by trickle in tap water.

    I can then add ST on a regular basis, as per Freddyboy - 3 days for 1 litre per 2 minute trickle.

    Thoughts?

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  24. #16
    Quote Originally Posted by DFC1980 View Post
    Hi All,

    Question, I intend to have a trickle feed running into my Nexus 220 as per below video:

    https://www.youtube.com/watch?v=rp0UNEnZHuE

    If i was to position the trickle inside the nexus near to where the water is sucked out of nexus by pump exit would this effect my bio area of nexus?, don't want to undo any bio build up by trickle in tap water.

    I can then add ST on a regular basis, as per Freddyboy - 3 days for 1 litre per 2 minute trickle.

    Thoughts?
    i had mine running into exit on nexus with pump just after exit for about 10 months. used dp4 tablets on sample from there .found traces of chlorine. and that was with 3 pod de chlorinater. plus st in pond
    i don t know if it affected my bio mass in nexus outer chamber. so to make sure i moved it to trickle into pond or skimmer. i now trickle into top pond.

    you could try it there and put your ST in the nexus exit. test it for a couple of days. and see if it keeps safe. but myself i was taking no chances.. at the time i was going through new pond syndrome as well.

    i like them fittings in the video for controlling the water speed. all the best fred

 

 

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