Okay. I will post at least part of this info once again.
Bleach aka sodium hypochlorite (not calcium hypochlorite) should NOT be used in aquatic water bodies especially in ponds where fish are for human consumption. The chlorine ions react with DOCs (dissolved organic carbons) or organic substances which are prevalent in natural waters. The various chlorine free radical reactions as by products form trihalomethanes a group or family of fat soluable chemicals that are bioaccumulative in the environment (move up the food chain). Relatively new scientific research has shed light on this chemical topic. For more info search it out on the web.
Trihalometehanes (THM, or TTHM - total trihalomethanes) contain such chemicals as Chloroform, Bromodichloromethane, Bromoform, Dibromochloromethane; all suspected problematic toxins in one form or another as they accumulate or deposit in the tissues of humans from eating contaminated fish who got them from the food web.
Since chlorine is a very common additive to public water supplies, THMs are also now a concern of municipal water plants and the EPA as they mandate and monitor public water testing. NORMALLY formation of trihalomethanes is not a real big concern of potable water since chlorine is added in the final treatment process where often, but not always, the presence of dissolved organics (DOCs) is not very high. Water as in natural waters with high DOCs definately form proportionally more trihalomethanes when exposed to free chlorine ions (bleach). Water treatment plants are always mindful and concerned of this feature. Water from wells usually contain few if any DOC's or bacteria thus the need for chlorine is minimal or nonexistant.
Thus adding chlorine to natural waters almost always creates relatively or comparatively large amounts of THMs that are stable in the environment and bioaccumulative. Adding reactive chlorine ions to natural waters is a very environmentally unwise practice. Don't blame ignorance if you or someone you love gets some sort of illness later in life from eating THM contaminated fish or aquatic life. Often it is not just the THMs that are a problem, it could be the synergistic affects of variouis THMs reacting with other chemicals as the body ages.
Why create unnecessary toxins when trying to eradicate unwanted fish? Is the enviornmental damage to your pond ecosystem and the resulting health risk worth doing it improperly based on todays scientific evidence.
One of the problems is that old outdated literature does recommend using chlorine to eradicate fish. HOWEVER new technical information does not support this philosophy.
Chlorine does have a valuable place and use in society, but its use in natural waters to eradicate fish is IMO NOT very responsible or wise especially when there is a perfectively safe alternative fish toxicant (rotenone) that relatively quickly deteriorates or can be made to breakdown very rapidly into benign compounds that are not bioaccumulative.
Last edited by Bill Cody; 02/20/09 02:35 PM.
