Bob replies...

Dear Craig,

Thanks for a very interesting post and I don't want to get into a 'mud slinging' contest! (sorry for the pun!) As for the mud-type refugium, I think they are fine for fish-only systems, however, I have a different opinion when it comes to their use on reef systems. As you probably know I don't sell aquarium products - never have and never will. I speak from past experience (57 years of aquarium keeping, and note, I've never been paid to say nice things about any aquarium products).

In all honestly, when someone sells or distributes a product, they have a financial interest in its wellbeing. I've seen products come and go, and I think mud systems will be one that will wear out their welcome in a few years. I find it difficult to understand why a hobbyist would want a mud/swamp like environment that is rich in hydrogen sulfide and probably also contains some methane, attached to their reef system. Why have a nutrient rich system attached to a nutrient poor system! Algae scrubbers did not work for reef systems, and I predict mud systems will go the same road.

With that said, I had an opportunity to visit Leng Sy's shop in Irvine California and see firsthand the level of success he was having with his Ecosystem/Miracle Mud. There was no doubt his mud system refugia teamed with life. In fact, I preferred to look at his refugiums than his main systems! His bare-bottom main systems were quite healthy looking, however in my opinion not as healthy as what the more environmentally microbial balanced plenum system/Berlin system can offer. Yet, the 'degree of success,' is in the eye of the beholder, so to speak. We had a backroom chat, and delved into various topics. I came away convinced this was a 'bump in the road' endeavor, and not based on sound knowledge of microbial processes. And, without the help of Mike Paletta, a good friend of Leng, I doubt it would have proceeded this far. And, since there's a lot of money to made in selling the mud product, it's a method that will be touted by those benefiting from its sales.

One of the numerous thoughts presented that I don't buy into is that there is competition in these mud systems for nitrogen compounds between the bacteria in the sandbed in the main system and that of the Caulerpa in the refugium. However, the word "competition" is a misnomer.

The destructive denitrification process in the sandbeds anoxic zone would be supplied nitrate from the above mineralization and nitrifying bacteria in the oxic zone of the sandbed. Since the diffusion gradient is controlled by electrical charge, it's not possible for it to 'compete' with the Caulerpa in the refugium. However, Caulerpa will normally absorb some nitrate from the bulk water and slowly break it down to ammonium for growth. However, most of the Caulerpa needed nitrogen supply would come from the ammonification process in the mud. That's because most of the mud particles are so tiny its porewater 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 from the bulk water and wasting its energy to break it down. It would simply be supplied a readily available amount of ammonium, which is what it really needs for growth, directly from the mud. And since Caulerpa does not have roots, its evident that ammonium is leaching up into the bulk water of the mud bed.

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. In all honestly, mixing the two methods in one aquarium is an ill-advised approach. You are probably aware that the best phosphate removing compounds, such as ROWAphos, is an iron-based product. Iron, in the substrate also attracts phosphate, and when the sulfur/sulfate processes occurs in the bed (a very normal process and always occurring process in sandbeds), the iron is oxidized and the phosphate is released. Some of the phosphate's oxygen molecules are utilized in surrounding processes producing phosphorous, however, some phosphate probably also leaches into the bulk water. Good for algae growth!

As you may also know, carbon is a player in how well inorganic nutrients, e.g., nitrogen and phosphorous are utilized. Mud/fine sediment and/or deeper beds tend to store more carbon, whereas courser sand cycles carbon. This in turn relates to how the type sediment/bed supplies heterotrophs and autotrophs their essential foodstuffs. Heterotrophs are mostly responsible for breaking down organic matter and prefer areas where diffusion abounds and where carbon is well cycled. Autotrophs, such as cyanobacteria, prefer an abundance of carbon. Since heterotrophic bacteria are the mainstream inhabitants in our sandbeds, should they be limited by carbon and inorganic nutrients it would have a negative impact on their neighbors and the microbial food web. Therefore the ratios between carbon and nitrogen, and that of phosphorous are very important issues when facilitating population densities of either bacteria. And those densities are very important to 'long-term' success.

And, the comments made that iodine is liberated into the bulk water is, without question, poor information. I'm convinced from the looks of Leng's tanks that unwanted iodate, not the more useful form of iodide, was in over abundance. (This is a long story, but you hopefully get the point.)

Of course, bio-load and on-going husbandry/water changes play a major role in any type system, however, small mud-like add-on systems need some forethought as to their application.

And, running closed system aquaria without a quality skimmer, is without question, another one of those 'blips' on the radar screen. Here one day and gone the next. A not too well thought position, as system oxygen content/redox benefits alone are indispensable for most marine systems. And, with excellent plankton additives on the market, such as Marc Weiss Spectra-Vital and BlackPower products, the attention to closed system naturally generated plankton levels is far skewed, and in my opinion, falls more into product hype than anything else.

As to refugium size, it's their purpose that relates to size, and of course the space to contain them. Without a doubt, the larger they are, the more water there is to diminish overall poor water quality problems. Yet, that's like saying I'm not going to take care of myself because there's always a medicine to cure the situation. And because you don't mention your environmental goal - fish-only or reef system, it's difficult to recommend a refugium size. But keep in mind a refugium is 'another' tank to care for. The larger it is, the more care it will need. All I can say is that I would have the largest one possible that fits the available space, no matter what the goal. It can always serve as a separate quarantine or hospital tank if needed. And, since I never did get to see your sketch, would suggest a bed of fairly course sand, something in the range of 4 -8 mm, with a depth of about four inches in the main system, where you can enjoy your digging fishes.

As for US magazines, there's two major publications I can recommend - Aquarium Fish (www.aquariumfish.com) and Freshwater and Marine Aquarium (E-mail: FAMAMAG@aol.com) . Check them out, and I currently have a column in FAMA.

Hope this suffices, and if you have any further questions, don't hesitate to contact me,

Cheers,

Bob Goemans