Water from public supplies (i.e. city, county) will contain one of two chemicals to prevent water-born diseases.  The first chemical commonly used is a small amount of chlorine.  Chlorine will evaporate out of water within days to hours depending on the concentration level and amount of aeration.  To lengthen the time chlorine stays in the water, some suppliers will use chloramine which is a compound of chlorine and ammonia.  Of course we do not want either chlorine or chloramine to enter our ponds.  All of us should be using a dechlorinator when doing our weekly 10% or more water change.   

The most basic, least expensive, and safest dechlorinator is the compound sodium thiosulphate (ST).  ST comes in milky crystals that look like oily rock salt.   ST will neutralize chlorine on contact.   If the water contains chloramine, ST will break the chlorine-ammonia bond.  ST will then neutralize the chlorine.  What happens to the remaining trace of ammonia?  It is handled by the pond’s filter the same as the ammonia being produced by the koi.  

When should we use ST?  Anytime we do a water change where there is a working filter and the source water contains chlorine or chloramine (i.e., virtually all public water supplies).  Note we said where there is a working filter.  Something has to eat the ammonia!!!!    If you are setting up a new pond or a quarantine facility you may not have a working filter with bacteria ready to eat ammonia.  In such a case, consider using a commercial dechlorinator product such as a Amquel + or ChloramX that will breakdown or bind the ammonia.   ST will do nothing about ammonia. 

What do I need to make some of this ST dechlorinator?  You need:

• An electronic scale such as used for cooking to measure ST crystals by weight

• One plastic contain (1 quart or one gallon) for making and storing dechlorinator (don't use glass around pond!)

• One quart or 1 gallon of distilled water or tap water (depends on how much dechlor you want to prepare)

• 125 grams (4.4 ounces) of ST crystals to make 1 quart of dechlor or, 500 grams (17.6 ounces) of ST crystals to make 1 gallon of dechlor

To make and use dechlor:

• measure 125 grams (4.4 ounces) of ST and place it in a 1 quart plastic container or, measure 500 grams (17.6 ounces) of ST into a 1 gallon plastic container

• add distilled or tap water to fill the container (1 quart or 1 gallon)

• mix the crystals into the water; they should readily dissolve

• use one liquid ounce of the dechlor for each 295 gallons of tap water to be dechlorinated

Your quart of dechlorinator should handle ~ 9,463 gallons of tap water.   A gallon of the dechlorinator should handle ~37,850 gallons of tap water.  Store any unused ST crystals or dechlorinator solution in a cool dark spot.   Neither the crystals nor solution needs refrigeration.  The shelf life of the crystals is many years long.  Naturally keep the ST crystals and dechlorinator solution out of the reach of children and dry pets.