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