Like I said in a previous post, I believe that the MM system "works" because of how it is setup. According to Leng's website, the first portion of the "filter" is a chamber that contains bioballs. Now most of us know that a wet/dry with bioballs is a "nitrate factory" but it does a good job of breaking down wastes pretty quickly but causes a nitrate spike. The next section of the "filter" is an iron rich substrate. This substrate has about 1/4 of the iron (Fe) of laterite, approx 36,000 ppm or 3.6% Fe (laterite has about 110,000-120,000 ppm Fe or 11%-12% Fe). This is a HUGE amount of Fe -- even compared to many of the freshwater planted substrates for planted tanks (it was 5th highest on the link I posted earlier).
Now think of fertilizing a garden/yard: you need 3 primary nitrients N
:K (nitrogen : phosphorus : potassium) and extrapolate that to fertilization of macroalgaes. The bioballs (breakdown of food, wastes, etc) provide the nitrogen source, food provides the phosphorus, and natural saltwater has *plenty* of potassium. Plants and algaes need a certain amount of Fe for optimum growth as well and the FW planted people have been using Fe containing substrates for many years. I believe Leng extrapolated this into saltwater aquaria and is using an Fe rich substrate for this exact purpose: aid in macroalgae growth.
This is all anecdotal evidence from here on out, but I've talked to / read about a couple people that have added laterite (an Fe rich clay) to their aragonite sandbed or started dosing with liquid Fe concoctions and noted a marked improvement in their macroalgae growth (I believe it was Delbeek that was playing around with laterite in with some of his seagrasses at a previous MACNA and showed an improvement in their growth?). Before this event they were having problems with either nuisance algae and/or poor macroalgae growth.
An interesting experiment to verify what James has been asking all along (is it the MM that is working in the "filter" or would a DSB/aragonite do the same thing) would be to setup 3 different tanks: one w/ MM, one with pure aragonite, and a 3rd with aragonite + laterite at a known concentration. Detailed observation of the tank and the macroalgaes would of primary interest.
An interesting thing that I've heard a couple people say on chat is that if MM contains high concentrations of Fe that maybe the reason corals show a marked improvement is that they need some trace amounts of Fe for their zooxanthellae to flourish along with trace amounts of nitrogen from the bioball section. Dunno about this. Maybe Borneman could comment on this supposition.
Anyhow, FWIW,
liquid
[ October 01, 2001: Message edited by: LiquidShaneo ]