matrix doesn't have bacteria in it, it has to be cycled. actually double cycled. first for the aerobic bacteria, then for the anaerobic. it's supposed to reduce nitrates because when the aerobic bacteria colonize the outside, anaerobic bacteria colonize the inside. they use nitrates for energy production instead of O2.
when I look at amazon's listing for a 5G bucket of matrix it says-
Product Dimensions: 12.5 x 12.5 x 19.8 inches ; 22.4 pounds
Shipping Weight: 47.2 pounds
I don't know where they get the 22.4 lbs from but the shipping weight is pretty close to what I weighed it at.
and it is made by seachem, the logo on the bucket is too small to see in the pics.
matrix may look and feel like rock, but it isn't. it's sintered glass. it's hollow passages throughout the entire media. which allows multiple types of bacterial colonization. which is why it's so light.
interesting info, I'd like to see your sources.
give this a read.
http://www.google.com/url?sa=t&rct=...psH7CA&usg=AFQjCNFTcD0ywxm9C66GYQP32Q2tEtGb4w
according to that, matrix in the same volume as the compared substrates, has much more surface area. granted, it is put out by seachem, but I don't see anything similar from fluval or eheim. the chinese spec sheets for ceramic media that I've seen back this up with lower surface area numbers and higher densities.
