"zookeeper" wrote in message
...
When we inherited our pond (from previous homeowner), two 50gal barrels
were full of red lava rock, and the third had a large rolled piece of
filter "batting." We kept the rock through the first year, but it was
too heavy to remove or stir when trying to clean. We refilled the "rock"
barrels with strapping tape (courtesy of the boys' paper route bundles)
which is much easier to stir and rinse out once a year.

Forgive me if this is a naive question...is the material in the filter just
a matter of surface area? I thought the lava rocks had some filtering
property.

BV.