actually, all gravity type filters allow good oxygen into the media no matter what
the material is. Ingrid

Sean Dinh wrote:
One thing great about TT is that the water get good oxygenation from flowing
down non submersed lava rocks. Do you suspend the screening horizontally as to
replace the lava rocks? Or are the screenings submersed? If the former, how many
layers do the water fall through before hitting the water level?

K30a wrote:

Actually don't buy lava rock - too heavy, too hard to clean.
We use black vinyl screening. 50 yards for a 3,000 gallon pond. Clean once a
year - easy. Always smells river water sweet.

k30a