which dechlorinator is best for koi pond top-offs?

Question
I have a 1000 gallon koi pond, 6 months old.  The installer gave me some
Sodium Thiosulfate crystals to dechlorinate when I top off the pond, or do a
partial water change.  It has worked well, but I can't find a source from which
to purchase more.   Can you recommend a chlorine neutralizer I can buy
retail?  There are several brands... and some seem to neutralize more than
chlorine/chloramine.  Thanks!

Answer
Hi Mary: I would start by understanding the contents of your tap water. Contact your local water department and ask them if they treat the water with more then just chlorine. If your tap water just has chlorine then all you really need is a dechlorinator... or a product that will take out the chloramine as well... What I have always done is to keep two or three 55 gallon plastic trash cans full of water.  Within 24 hours they are naturally free of chlorine and I do not have to add chemicals to my pond... saves hundreds of dollars per year.  If you need further recommendations then let me know once you have contacted your local water department... then I can suggest to you a product or two that will meet your needs... dave