Unlike chlorine, which dissipates when water sits for a few days, chloramines may take weeks to disappear. If you don t want to use a dechloraminating chemical, the next best solution is to install a granular activated filter and allow sufficient contact time. This will depend on the amount of water added in relation to the size of the aquarium or pond and the time period over which it s added. An alternative is to monitor for a total chlorine residual in the aquarium or pond while adding the chloraminated water. Chloramines will have to be removed if the water used to make salt water solution comes from a chloraminated supply.
Chloramines affect salt water fish just as they effect fresh water fish.
Koi are just as susceptible to chloramines as any other fish. However, it must contain high quality granular activated carbon and you must permit sufficient contact time. Salts can be caught by the permeable membranes but chloramines pass through easily. Boiling is not an effective method of removing chloramines from water. The only practical methods for removing chloramines from water are using a water conditioner which contains a dechlorination chemical or by using granular activated carbon.