"George" wrote in message
news:JRP_d.83176$r55.40732@attbi_s52...

I completely agree about wet-dry filters, which is why my bioballs have
all been
cleaned and my grandchildren now play with them. I have been reading
about
Jaudert plenums, and it seem like it might be the way to go. And you
might be
right about using gravel instead of sand. The article mentions gravel in
the
range of 2-3 mm, which it pretty small, so that might work in place of
coarse
sand. It will definitely be easier to install in a 1,200 gallon pond.
Thanks
for the link. It helped.


No Problem,
As for the plenums, I run one on my system. I've heard debate on whether or
not they can cause the tank to crash. I think a simple remedy for this, and
one I've implemented is to put a series of airline tubing inside the plenum,
use tees to take the individual pieces and combine them into one access
line. Then bury the access line behind some LR. If you ever start having
problems with your tank, then you can syphon some water from your plenum and
check that. It will tell you whether or not your plenum is causing the
problem. If so, syphon some more water off, and the vacuum created will
pull more oxygen down into your sand, thus keeping anaerobic bacteria away.

This method is described in detail somewhere. I think I learned about it on
garf.org but I'm not sure. If I had some more time I would look the link up
for you, but I need to get back to what I was doing. -Chris