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What kills the fish? How might you reduce the fish mortality after raw sewage is accidentally released into a small pond containing large bass fish?

6 Answers
The dumping of large amounts of raw sewage into rivers or lakes can lead to large fish kills even though the sewage is not itself toxic to the fish. Similar fish die-offs occur in shallow lakes in the winter when they become covered in ice. What kills the fish? How might you reduce the fish mortality after raw sewage is accidentally released into a small pond containing large bass fish?
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For completeness what kills the fish is "eutrophication" (look up wiki).
Briefly is means that microbes in the water (from the sewage itself as well) eat the sewage and in so doing consume oxygen in the water. As we know fish "breathe" water but if it has no oxygen they die. In severe cases microbes will even convert oxygen in sulfate to hydrogen sulfide which anyone can recognise as a really bad pong. Eutrophication means literally "full of goodies" or too full in this case.

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When raw sewage is added to pond water,the water gets nutrients,especially phosphates & nitrates which gives rise to phytoplankton blooms.This mass of phytoplankton will consume good amount of Oxygen during night time & can make it nil,when the fishes in the pond dies.If the sewage is released in a pond in very small doses over a time period in such a way that there are no phytoplankton blooms,then the fishes don't die.Immediately it can be corrected by addition of quick lime .

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I think that lime would help this but it would also increase weed growth, lime neutralizes the raw sewage and it would take a few bags to do this also, like 50 lb bags from a garden or farm store!heres a site that will help you decide what amounts !! and wehat kind . you need to have a pure lime product!
http://www.agfc.com/fishing/fish-management/farm-pond-management.aspx

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Wristb34 is correct. The raw sewage has the potential for aerobic bacteria to make the water anoxic (deviod of oxygen). In addition, the exotoxins secreted by the bacteria do their damage as well.

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Either polution or global warming.

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Pollution

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