BV,

All of the diffusers that I have seen are just airstones. Some of the
bottom drains are made with an air diffuser attached to the dome of the
bottom drain. The diffuser causes an additional water flow, upward over the
bottom drain, in effect creating a higher bottom surface current. You could
probably use any air stone mounted on top, or take a piece of poly tubing,
plug one end, and drill a series of holes in it and mount it to the outside
edge of the bottom drain bell.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"BenignVanilla" m wrote in
message ...
"Lee Brouillet" wrote in message
...
No, the bowl is the "dome" over the open drain. The air diffuser is
mounted
to the top (or bottom, depending on how you look at it!) of the dome.

Remember, I didn't purchase a commercial bottom drain: I made it from a
toilet flange. Therefore, it's just a big open hole in the ground that
needs
to be covered to prevent the vortex action. That's where the 16"
terracotta
bowl comes in. If you already have the bottom drains, and merely want to
convert them, go to Mike Singleton's site and go through his DIY
section;
there's an article there about making a conversion to a Tetra bottom
drain:
http://www.livingjewels.com

I plan on building a DIY bottom drain...my original question was about a
bottom drain that included a diffuser. I have no idea what a diffuser is.

BV.