"robv60" wrote in message
oups.com...
I do have a reservoir at the top of the stream/falls. Not very deep
though, only about 8 inches deep. Im also concernd about water pressure
loss to my stream/falls using too big of a filter, hence the want to
filter through rocks in the streambed.


Depending on your filter design, it doesn't necessarily have to cause a loss
in pressure. A mechanical filter that is inline may cause pressure loss. An
8" deep area isn't deep enough to expect any sort of settling chamber.
However it maybe deep and wide enough to build a bio and veg filter there.

Using furnace filter material, scouring pads, etc, arranged such that there
is plenty of water flow through or around it. Don't just stack it on the
bottom. Then plant watercress, waterhyacinth on top of it. The roots will
filter out all the nutrients and the sediment settle out.

-S