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Gravel as a true filter media
>A table of media surface area per unit volume in Vol. 1
>of Baensch's Marine Atlas shows that small-grain gravel
>has roughly the same surface area of commercial plastic balls
>and ceramic cylinders (but much less than sintered glass).
>I would like to know if anyone uses gravel in their (canister)
>filter in place or, or with, commercial media.
I've used gravel in my canisters for years. But I don't use the small
grained stuff for several reasons. First, it compacts too badly, second,
the small pieces can escape the media container and too easily damage the
impeller. Third, I'm not really looking for much in the way of bacterial
filtration anyway... my plants are the biological filter for the tank. I
just want something to keep the the media basket from collapsing from the
suction of water running through it. My favorite gravel for this purpose
is Estees Natural Aggragate. It is large and round, almost polished
looking. Actually, it would be really pretty gravel to use in a tank if it
weren't so darned expensive. But you need less than a 5 lb. bad to fill a
canister filter, and it's a one time purchase. It's a lot less expensive
than commercial bio-materials!