Chlorine and Koi. Neglecting to control chlorine in the water in a koi pond can result in the death of the fish. Water treatment plants add chlorine to water to remove bacteria and parasites so the water’s safe for human consumption and doesn’t pose a threat. However, to koi, chlorine is toxic.
Chlorine helps make our drinking water safe, but can cause all sorts of issues for ponds and fish.
Chlorine is necessary in our mains water to control harmful bacteria growth which can easily make us sick if left untreated. Chlorine in low quantities isn’t harmful to us in tap water, but can still be easily removed by letting water stand or boiling it using a stove or kettle. Since chlorine is a gas by nature, it will slowly evaporate into the atmosphere as tap water stands and gas bubbles reach the surface.
Even though chlorine is unlikely to cause any problems for us, it can cause all sorts of issues for animals more sensitive to the chemical – such as koi and goldfish. Chlorine is toxic to most aquatic life, and it can cause stress and nasty burns to pond fish once it enters the gills. Chlorine heavy water should always be treated for ponds with fish, especially if you’re performing a particularly large water change.
Luckily, chlorine and it’s derivatives (see more below) can now be easily removed from mains water via several different methods; these include dechlorinator treatments, activated carbon, and dedicated filtration units. All of these options can remove residue chlorine making water much more comfortable and safe for goldfish, koi, and the rest of the pond’s eco-system.
What is the difference between chlorine and chloramine?
Water companies may be using either chlorine or chloramine to disinfect tap water, and both need to be removed.
For the longest time chlorine was the disinfect method of choice for water companies, but in recent times a newer substance has emerged called ‘chloramine‘. Chloramine is a mix between chlorine and ammonia, forming a new compound which lasts much longer than chlorine and does not evaporate into the atmosphere. This is great news for water companies, as it means they can more efficiently treat tap water and it remains disinfected from bacteria for much longer. However, this is bad news for pond owners as it means you can no longer just let water stand to remove the substance, and many older water conditioners only remove regular chlorine, so chloramine would still remain.
The solution? Making sure your dechlorinator treatments can neutralize both chlorine and chloramine. Newer water conditioners will easily remove both substances, so if you’re unsure which chemical is used to disinfect your tap water, it’s often best to go with a dual-treatment option to be safe. If you want to double check, you can also call your local water treatment company and ask what chemicals they use in their treatment process. Some counties and states will continue to use regular chlorine, but others may have started to adopt the newer chloramine treatment method – only way to know for sure is to ask!
Why is chlorine dangerous to ponds and fish?
Both chlorine and chloramine are deadly to aquatic life, causing burns, stress, and even death.
Chlorine and chloramine are highly reactive substances that easily bind and react with organic compounds. Chlorine in sufficient doses is a highly effective disinfectant, which is why it’s used globally in mains water to destroy bacteria. The problem with this is the chlorine will not be able to distinguish between “good” and “bad” bacteria, and will quickly kill off all types of bacteria in your pond and filter box. Beneficial bacteria which are essential to a ponds biological filtration will also be destroyed by chlorine, which would result in a drop in water quality and a spike in waste substances.
Chlorine and chloramine are also very toxic to aquatic life, with only small doses being needed to cause significant damage and stress to fish. Chlorine will cause burns upon contact, damaging the gills, scales, and breathing tissue of goldfish and koi. It also readily enters the blood stream after it passes through the gills, causing internal burnin