"Dick" wrote in message
...

What is "biological filtration"?


That the process where certain bacteria turn ammonia to nitrites, then
another bacteria turn the nitrites to nitrate. Both ammonia and nitrites
are toxic to fish. Nitrates are not unless excessively high.
--
KL....
Frugal ponding since 1995.
My Pond & Aquarium Pages:
http://tinyurl.com/9do58
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