On Wed, 13 Sep 2006 09:30:36 -0500, Köi-Lö $##$$@$##$$.#$$ wrote:


"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.



One does not filter "in" or "out" bacteria. Nitrates are not
biological, they are just chemcals. The bacteria are the active
agents.

Every pond is full of bacteria, all doing special things.

No filter, I can imagine, would be classified as "biological
filtration." Why would one want to filter out bacteria?

dick