Chloramines are a combination of chlorine and ammonia, both of which are toxic to fish. As chloramines break down, either naturally or through the use of dechlorination chemicals, ammonia is freed. This ammonia can be removed from fish ponds by using products available in the Water Quality Category. Biological filters, natural zeolites and pH control methods are also effective in reducing the toxic effects of ammonia.
Unlike chlorine, which dissipates when water sits for a few days, chloramines may take weeks to disappear. When adding even a small amount of water to your pond from municipal sources, you should monitor for total chlorine residual. Chloramines residuals in water used to keep fish should be kept below 0.1 mg/L. Total chlorine test kits are available in the Other Helpful Products Category. Make sure, however, that the kit is for "total chlorine" or "combined chlorine," not "free chlorine." A free chlorine test of chloraminated water would read zero but still be toxic to fish.
Activated carbon filter may be effective in removing chloramines, however, it must contain high quality granular activated carbon and must be permitted sufficient contact time with the water.
To find products to help treat ammonia buildup, check out
> Water Treatments > Water Quality.