Bob replies...

Hi Mike,

Thanks for your email, and you may want to checkout my website at saltcorner.com for fair and well-balanced information on many different subjects.

As for your question, I think the answer centers on just what are your goals for the system. If your going to be running a system tuned to high quality water for the more reef crest type stony corals where little or no algae is present, then the plenum method is unbeatable, however, should be used in an interconnected sump-like tank. If your goal encompasses more bay-like corals where undesirable type algae is more commonplace, than the mud system may be the way to go.

Below is my comment sent to another reader; As for Leng Sy's device, I had an opportunity to visit his shop in Irvine and see it firsthand. There was no doubt his mud system refugia teamed with life. His main systems were fairly healthy, however in my opinion not as healthy as what the more microbial balanced plenum system can offer. Yet, success is in the eye of the beholder so to speak.

Bear in mind the all important destructive denitrification process in the anoxic zone is supplied nitrate from the above mineralization and nitrifying bacteria in the oxic zone of the bed. However, mud systems have practically no oxic and anoxic zone because the particle size of the mud is so tiny! Second, the diffusion gradient is also controlled by electrical charge and gravity, therefore it's not possible for a bed of any size particle directly on the aquarium bottom to function in any mode except that of a nutrient collection device because redox simply becomes more negative with depth. Not so in plenum systems. Third, the Caulerpa in his systems absorb some nitrate from the bulk water and slowly break it down to ammonium for growth. However, most of its nitrogen supply would come from the ammonification process in the bulk of his mud sandbed. That's because most of the mud particles are so tiny its pore water is almost nonexistent. Therefore it harbors the ammonification form of denitrification throughout most of its bed, liberating generous amounts of ammonium. So the Caulerpa would not be dependent upon getting nitrate and wasting its energy to break it down. It would simply be supplied a readily available amount of ammonium, what it really needs for growth, directly from the mud. Also, Leng's system uses a mud that is high in iron. Iron, in any type sandbed system whether a plenum or directly on the bottom, is instrumental in phosphate releases because of the processes associated with the sulfur/sulfate process.

If you have any further questions, please contact me.

Cheers

Bob