Jim,

The design that Joe refers to says:
"You can buy plastic beads for your filter from plastic suppliers or Aquatic
Eco-Systems (part AB1 - Filter Beads). Get enough beads to fill your drum
half way (2 cubic foot for a 30 gal drum, 3.5 cubic foot for a 55 gal drum).
Be sure to get beads that float."

The example I refer to uses sand rather than beads, Coral sand is much
smaller than beads and has a good surface to allow bacteria to grow (but is
very abrasive - see problem below).

The advantage of the sand based one is that it grinds any solids up to
nothing and allows the bacteria to attack them at the microscopic level.
Some people have described sand based filters as good for "polishing" the
water.

I think you may still want some mechanical filtration in front to keep out
the bulk of the blanket weed etc that can go through a normal solids
handling pump. But anything that will go through the course mesh filter that
is often integral to a pump, or the home made planting basket pump cover
will be ok.

The sand version is also a lot smaller than a bead filter as its only a
vertical length of 4" sewer pipe rather than a 30 or 55 gal drum.

The only problem is that the sand will eventually wear away the walls of the
filter and it will leak and you will need to build another main tube. :-(

The bead design has a fine mesh on the inlet / outlet pipes so it definitely
needs to be after any mechanical filtration and simply provides biological
filtration.

Cheers

Gordon
long time lurker on r.p and now r.p.m


"Phyllis and Jim" wrote in message
oups.com...
Gordon,

Where do you get the beads?

Jim