Re: [APD] RE:filter or pump

["Thomas Barr" <tcbiii at earthlink_net>]

> > Powerheads with spray bars are good along the bottom back wall blowing
out
> > along the slope of the gravel.    
>
> Tom,
>
> I'm usually pretty good at following your logic, but would you care to 
> elaborate more here?
>
> -- 
> Craig Morrison

Spray bars evenly distribute flow across a wide area, simple single out
lets do not.
The lower back portion of a tank is typically covered with plants etc, so
this powerhead and spray are well hidden in most tank designs. 

The direction of good current going through the lower portion of the leaves
is a good flow pattern. This mimics currents in natural rivers/lakes and
also is a good pklace to introduce the CO2 rich water back into the planted
tank.

If you add CO2 rich water to the lowest parts of the plant shoot, the CO2
will rise up and come in contact with the lower underside(abaxil) of the
leaf wherew the stomata are which will allow the gas to be absorbed.

If you use a spray from above, the CO2 hits the top of the leaves and only
the top parts of the plant before the current is reduced in the thicket of
plants. The lower parts have trouble getting enough CO2.

The oldest leaves will be near the lowest part of the plants also. Current
will reduce most epiphytic algae that attaches to leaves and the oldest
leaves will have the most. 

This also adds some O2 and CO2 exchange along this gravel surface which
also acts much like bio media inside filters. Having current running over
the most shaded part of your tank is a good idea. This allows better
breakdown of waste and allows you to remove any large pieces of detritus
and plant leaves.

Regards, 
Tom Barr






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