ST Dechlorinator

How to dechlorinate pond water safely

Tap water is treated with chlorine or chloramines to make it safe for humans, but these chemicals are highly toxic to fish and beneficial pond bacteria. Using a sodium thiosulphate calculator allows you to neutralise these toxins instantly. Sodium Thiosulphate (ST) is the industry-standard dechlorinator used by professional koi keepers for its reliability and cost-effectiveness.

The difference between Chlorine and Chloramines

While standard chlorine can be gassed off with heavy aeration, many water authorities now use chloramines (chlorine bonded with ammonia), which are much more persistent. Our ST dechlorinator calculator uses a safety-first multiplier to ensure that even stubborn chloramines are fully broken down, protecting your koi's delicate gill membranes from chemical burns.

Dosing Sodium Thiosulphate

For the best results, always dissolve your ST crystals in a jug of warm water before adding the solution to your pond near the filling point. It is best practice to treat the volume of new water added during a water change, rather than the total pond volume, to avoid an unnecessary buildup of chemical residues.