Categories: Filters, Shellfish Tanks, Todd's Top Tips505 words1.9 min read

Why Are Chloramines Bad For Shellfish?


Errin Todd


February 23, 2017


Chloramine is a mixture of chlorine and ammonia and is being used more often in the UK to disinfect tap water.

We are aware of customers in London, Birmingham and St Abbs in the Scottish Borders where the local water authority add chloramines to the water for disinfection and we are sure there are other areas too.

Ammonia is toxic to shellfish.  Whilst chlorine in tap water can simply gas off if left overnight chloramines cannot be removed as easily.  If you have chlorine in your tap water and plan to mix this with artificial sea salt then use a separate mixing tank and only use after 24 hours when there is no chlorine.  We would still recommend using activated charcoal to absorb any chlorine left over.  The bond of chlorine and ammonia in chloramines however cannot be easily broken or removed by either leaving for 24 hours or boiling.  We can provide a chloramine filter which first breaks the chemical bond and then removes the chlorine and ammonia however this is extra capital expenditure which should be considered when purchasing a new system.

If you are using raw seawater in your shellfish holding system then this will have no real effect however be careful if you wash any equipment e.g. nets or boxes in the tap water and be sure to dry it before use.

We always recommend using raw seawater where possible as this is better and cheaper than using an artificial salt mix.  If you are too far from good quality seawater or safe access to the sea then artificial salt is your only answer.  We offer any prospective customer in this situation a free water test to check for chloramines.  It is your responsibility to check with your local water authority and be sure to specifically ask about chloramines in your tap water.  Be aware that some authorities can switch from chlorine to chloramines with no notice to you, their customer.  Sometimes after heavy rain or flooding ammonia can enter reservoirs from farm run off and this can bond with the chlorine that is added to give low levels of chloramines, so even if it not added by the water authorities it can sometimes find its way into our water.  A simple test is to leave a glass of water out all night and check if bubbles appear.  Chlorines gas off and appear as little bubbles usually around the edge of the glass.  Chlorine also gives off a distinctive smell.  Chloramines do not produce gas bubbles or have any smell.  We also notice when we drink water with chloramines in as we can get sore tummies and it tastes different (and in our opinion does not make a good cup of tea!)

If you need to use salt mix we recommend Ayr based Peacock Salt which has a salt water mix specifically for native shellfish.  Tell them we recommended them.

If you want more advice on using artificial salt or chloramines please call Keith on Tel 01383 820685.

Best Fishes,