A Baltimore City pipe filled with chlorinated water – left to flow for 72 hours into a Leakin Park stream – has caused a major fish kill.Yes, the amount of chlorine commonly used to disinfect drinking water is poisonous enough to kill fish. It's not harmful to humans or other animals who drink the water because our stomachs are much tougher than a fish's gills. And most natural waters contain enough organic compounds that will react with chlorine so that a small amount added to a lake or stream won't harm most organisms.
The Maryland Department of the Environment (MDE) confirmed to The Brew that it has found about 2,000 dead fish in a tributary of the Gwynns Falls.
They include white suckers, stonerollers, blacknose dace, longnose dace, creek chub, crayfish and – by far the most endangered species – American eel.
Canvassing the stream yesterday, The Brew saw mature eels, some 30 inches long, floating in Dead Run about a mile downstream from the pipe, located under the Ingleside Avenue bridge near Security Boulevard and Forest Park Avenue.
MDE spokesman Jay Apperson said the fish kill was caused by elevated levels of chlorination entering the stream from the broken pipe.
In my fish tank, which requires a couple of gallons of water a week to replace evaporation, I can add up to five gallons to the 55 gallon tank without bothering to dechlorinate the water, and the fish will be unaffected. However, if I change half the water (which I do periodically) I need to dechlorinate the water or the fish will be distressed.
I'm a little surprised eels hung around long enough to be killed.