Re: Filter Capacity ( Flow rates)

["S. Hieber" <shieber at yahoo_com>]

Madan Subramanian pointed out a complexity in calculating
how often a filter/pump turns over the water ina tank:

> If your Power head or pump is rated at twice the capacity
> of your aquarium
> ie.,
> an aquarium of 30 gal volume and power head of 60gal/Hr.
> capacity and this
> power head passes the aquarium water through a device,
> assume a UV
> stabiliser, that does not progressively get dirty unlike
> a filter for
> example.
> 
> Then in order to have 99.99% of your aquarium water pass
> through the device
> it takes 4.6 hours.
> 
> In case of a power head pumping through a filter which
> progressively gets
> dirty with time the time taken for 99.99% of the aquarium
> water to pass
> through the filter is 6.375 hours as the flow rate
> decreases with respect to
> time.
> 
> The more you know the more complicated it gets !!!!!.

Indeed.  And those rates assume a virtually homogeous
mixing of filtered and yet-to-be-filtered water.  Try
taking into account the fact that that condition rarely
happens -- now you're talking complexity!  Calculus anyone?

And then try to factor in that stuff in the aquarium that
you want to get into the filter moves around in the water. 


Then try to accomodate all this to the known optimum number
of turnovers per day -- uh, wait, no one ever really tested
that for that, did they?  I'm going back to the rule of
thumb.  Thumbs don't point precisely, but precision
sometimes gets me quite lost ;-)

Scott H.

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