Chloraminated water that gets into our storm drains and streams through lawn watering or other release is diluted enough that it will not harm fish. Monochloramine is already entering our storm drains and streams as the Merklin reservoir has been treated with monochloramine since 2010.
Fish do absorb monochloramine directly into their bloodstream through their gills which, at higher levels of concentration, can damage the gill tissue and enter the red blood cells causing a sudden and severe blood disorder. For fish owners, monochloramines can be removed from the water by using a water conditioner. Your pet supplier should be able to provide any further guidance you may need on these products.