Chloramine is a combination of chlorine and ammonia and many people feel that treating water with this, rather than chlorine alone, gives an improvement in taste. Chloramines are both safe and well-established as part of water disinfectant treatment, they have been in use in the U.K., the United States of America and Canada for decades. Chlorinated water is safe for bathing, drinking, cooking and all uses we have for water every day.

However, there are drawbacks with its use, and people requiring kidney dialysis, as well as fishkeepers, need to take special care.
Kidney dialysis patients must remove chloramines from water fed into their machines; in the dialysis process, water comes into contact with blood across a permeable membrane. Chloramine, like chlorine, is toxic in this context and must be removed.

Removal can be done by adding ascorbic acid or using granular activated carbon (GAC) treatment: this is the responsibility of the medical centres operating dialysis treatments. Patients with home dialysis machines should check with their local renal unit who will recommend the appropriate type of water treatment.

Fishkeepers also need to remove chloramines from water used for aquariums -
either directly as in freshwater tanks and for water used with salts to make up synthetic seawater for marine aquariums. Although chlorine is also toxic to fish, it disappears rapdily, especially when fast water flow rates are employed: the turbulence blows off the chlorine and vigorous aeration will do the same.
Leaving water to stand for a few days also dispels chlorine but chloramine treated water won't respond to any of these treatments - chloramines may take weeks to disappear.

Dechlorinating agents, available from your aquatic stockist should work as well for chloramines as they do for chlorine; alternatively a GAC filter used at a slow flowrate (to allow sufficient contact time) is the next best thing. Always follow the instructions given with dechlorinators and carbon filters as closely as possible.

Chloramines affect the fish directly because it can come into direct contact with their bloodstream through their gill membranes. A peculiar anomaly is that whilst chloramine (an ammonia-based combination) is toxic to fish, they are apparently not affected by the ammonia they excrete naturally themselves from the very same gills during respiration. Ammonia can be produced too when chloramines are chemically removed but this may be subsequently removed by biological filtration, the use of zeolite and some pH control methods. Reverse osmosis will remove salts from water passing through its permeable membrane but chloramines pass through easily and are not trapped or removed.

During partial water changes, or topping up for evaporation losses, chloramines are still added although their amount depends on the proportion of new water added to the overall aquarium or pond volume. Chlorine residual levels can be monitored during water changes; these test kits are available at aquatic dealers or, alternatively swimming pool supply stores.