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Water thru Hardwood Charcoal = LYE. I wouldn't use it. I beleive most
aquarium safe charcoal is made from bone. ALSO....I have one hose from my
pump which goes thru the veggie/bio/mechanical filter that drains to the
waterfall...then another hose that just goes to the waterfall and not the
filter. Lava rock eventually clogs up I know from experience. I use 3M
floor scrubber mats about 6 of them and water parsley in my 60 gallon
filter. I also have a cleanout on the bottom side of my filter to
occasionally flush out sludge. Mats are cleaned once a year with dechlored
water. Works for me..has for 10 years...MIKE


I don't know what kind of lava rock you used, or the application, but mine is
used for biological filtration only, not mechanical filtration. It hasn't
clogged so far (I've used it for about a year). My experience with 3M mats is
that they clog fairly rapidly. I have the same experience with them in salt
water tanks.