be sure the return pipe is a large diameter and frankly, it works better to plumb a
biofilter in reverse, the input at the bottom, the output at the top just because
"crud" can settle on the bottom easier. OTOH, it IS easier to lift the coarse filter
off the top to clean it, but if you have an valve at the bottom that can be opened
then the whole thing is easy to clean out.
you not only need holes to make sure it doesnt clog, the more holes the less suction
at any one of them. Ingrid


On Mon, 24 Sep 2007 15:18:02 CST, bob29 wrote:


I have built one where the water flows in from the top via a spray bar,
through foam matting and filter material. The return pipe comes
vertically from the near the bottom of the tank, bends 90 degrees near
the top of the tank and returns the water to the pond. Question:How
far from the bottom of the tank should the bottom of the pipe be, and
should ther be any holes drilled in further up?