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Re: [APD] if power goes out, how long before bacteria die off?

I do not know  the biology behind what I'm saying  and its purely based on my understanding of the world.

It seems the bacteria will die quite quickly when there is a lack of oxygen. The lack of food Ammonia
 or Nitrates are not that important in the short term. So when the power fails the lack of O2 is the 
most likely killer of the bacteria.

The actual size of the bacteria colony and the type of filter will greatly influence how long they will last.

In  a heavily loaded system there will be a larger population of bacteria to cope with the day to day
Ammonia reduction. And when the power fails it will use up all the available Oxygen quite  quick.
So the bacteria will start to die much faster. 

Canisters - will deplete the supply of oxygen fairly quickly. And there is no way to replenish the 
oxygen supply.

Internal box filters  and under gravel  filters should last slightly longer since diffusion can take place
 to supply small amounts of O2 to the filter. They will also still provide some filtration around 
there edges while there is no power

External hang-on filters and trickle filters have an advantage that even during with a power failure
the bacteria will have more than enough O2 available to them. So they should survive quite easily 
until the thin water layer dries up. It most cases this could take several hours or even days. The 
filter is useless while there is no power but the bacteria will survive until the power is back.

Natural - Plants / live rock / plemium will keep on working regardless of the power failure and is
perhaps the safest of all. Especially in marine setups that use live rock or plemiums, where the filter is 
all natural, part of the display and not powered by pumps.

So filter performance during a power failure from worst to best is:

Fluidized sand
Internal Box
Under Gravel
External hang-on
Natural - Plants / live rock / plemium

This is all based on the assumption that the bacteria die due to a lack of oxygen. 

I have had a tank using a trickle filter with out power for more that a day with no. Ammonia spikes afterwards.
The ammonia spiked during the power outage but recover quite quickly when the power was restored.

Phillip Grobler
Cell: +27 083 654 0250
Instant messaging:
MSN: pfgrobler at hotmail_com
Yahoo: pfgrobler at yahoo_co.uk
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