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RE: "overfiltered"

James Purchase wrote:

>No matter how much volume (or area) your bio-filter has, you will NEVER
>more bacteria in it than is necessary for the amount of ammonia and other
>waste products being pumped through it. Bacteria, like all living things,
>require food and without it they will not reproduce and eventually their
>numbers will stabilize at a point where each bacterium is able to get only
>sufficient food for its needs.

I am fairly sure that this is not true. Like other living organisms bacteria
can adjust to food availability by altering their intake and metabolism. A
fixed population of bacteria could survive just fine on X amount of
nutrients, and if the nutrients suddenly increased to 5X they would increase
their nutrient utilization to use the increased food supply (assuing
sufficient O2 etc). I agree you cannot have "too much" biological filtration
in the sense that it would be actively harmful, but you could have too much
if the bacteria in your cannister are consuming nutrients that your plants
could otherwise use.

>People who advocate running "filter-less" tanks are not actually doing away
>with the bio-filtration.

Technically this is true of course but it sort of begs the question, which
is not whether a tank can exist without any ammonia-consuming bacteria, but
whether you can have a healthy tank without mechanically added biological

Another factor to consider it what happens during a power outage. It has
never happened to me, but I understand that the bacteria in a filter can die
because they are deprived of O2. When the filter starts up again the
material pumped into the tank can be toxic. Does anyone know the details or
time course of this?

Peter G. Aitken