Thanks for the interest. That was the first video made for reefvideos.com, so we learned a lot too. Unfortunately, I jammed too much info in a short segment. Hopefully reading this post will answer some questions and perhaps raise some new ones.
I'm not selling anything here, just sharing ideas. I'm still playing around with the design and would love to hear other members input. I based my concept on the naturally occurring conditions found in successful, well established, reef aquariums. It's kind of a modified chaos theory. I realized that benthic invertebrates and aiptasia anemones found a niche in the captive reef ecosystem, and were thriving. Clearly they had a viable nutrient source; one that was a byproduct of nutrient import, and resulted in nutrient export or at least assimilation/dissimilation.
The idea isn't entirely new, but an evolution of somewhat problematic concepts from Dr. Addey, Steve Tyree, Jaulbert, Leng Sy, and anyone else who has tried to harness nature to export nutrients.
The crux of the concept is to design a sump that is compact and concise, using nature-based technology. The first idea is to skim surface water from the aquarium, rich in surfactants (surface active/hydrophobic agents). Nothing new here; however, you would be surprised how many overflows actually draw water from below the surface, or allow for dead zones at the surface. A simple test would be to see how long it takes for floating flake food to overflow to the sump. Even coast to coast surface skimmers can be fallible. The most common design flaw is having the return, or closed loop effluent push away from the overflow teeth. Play around with your flow until you can have it push surface water from the opposite end of the display tank to the overflow.
Now that we've accomplished this, we have "pre-skimmed", protein-rich, water to process. The first zone in our system can actually be located in the overflow box itself. I discovered by accident, that aiptasia anemones were great mechanical filters and water polishers. The aiptasia anemones in one overflow I observed looked more like rock anemones, due to the perfect living conditions they found. They had diffused lighting, no competition, and a great opportunity to grab freshly imported and skimmed nutrients (fish food).
I thought I really had a contribution to reef keeping methodology, until I came across the same idea referenced in Anthony Calfos' book. I recently built a four foot tall tank, with an overflow from top to bottom. I'm not a big fan of deep sand beds, certainly not when they're fed a carbon source, but I was willing to experiment with a passive denitrifying bed. The four foot box allowed me to put a two foot deep, fifteen gallon, sand bed as the bottom half of my aiptasia zone overflow box. I ran a 1" perforated nylon pipe from top to bottom in the sand bed. The idea was that I could use this to test dissolved oxygen levels, add a carbon source (if something better comes along), and provide a passive water exchange. Placing a heater in the pipe would yield a very slow, controllable, thermal flow, as heat rises.
Back to the design. The protein skimmer is located in the first zone, called the "aiptasia zone". By zone, I simply mean segregated area. In our case, it's a small area with a dam overflow. The surface skimmed water is run directly through the protein skimmer if possible, or at least allowed to draw its' influent from the first zone only. The protein skimmer effluent is directed to the other side of our dam overflow to assure the water is processed only once. This is a very basic concept, but one that is overlooked in many sump designs.
The aiptasia zone is named as such for obvious reasons. Aiptasia are allowed to populate this area with the intent that they will act as a biological, mechanical filter. What I mean by this, is that unlike micron filters, aiptasia collect and reduce excess nutrients without having to be exported. Of course, once the population grows, you can and should harvest what you can for further nutrient export. For those who are not confident that their sump design can mechanically block aiptasia, or kill them through ultraviolet irradiation (UV sterilizer), xenia and or star polyps can be used in their place.
Now that we've established optimum protein skimmer function and mechanical filtration, we move onto the next zone for nutrient export. The refugium zone is where our skimmer effluent water is directed. A good sump design will have an equal amount of water pumped from the sump to the display, to the amount of water flowing through the protein skimmer. In other words, if your skimmer has a pump that moves 600 GPH, then the sump pump should have the same rating. This assures that all of the water entering the sump is processed by the protein skimmer. The refugium will also benefit by a slower flow rate such as this for optimum dwell/contact time.
The key design feature in the refugium zone is the shallow depth. For stability, we're working with chaetomorpha and or gracilaria in our model. The flow from the skimmer effluent and shallow depth will assure that these macro algaes will be detritus-free as they prefer. A shallow bed of macro algae will allow us to put another zone below it, thus the name "Duplex", but we'll get to that later.
The other reasons for a shallow (4-6") culture of algae is to optimize lighting and discourage die off. Conventional refugium design allows chaetomorpha to grow into a giant mass, with new growth at the surface where photosynthesis is possible, and older growth pushed deeper where light isn't available. This "old growth" is then allowed to slowly disintegrate and release its' nutrient catch (phosphate, silicate, nitrate, and heavy metals) back into the water column. Another poor practice is to harvest the algae at the top of the mass. This removes the efficient new growth, and leaves the dieing constituents behind.
Our upper level of the Duplex has only 4" of macro algae to worry about, so the whole culture is illuminated. Old growth is pushed to the sides where photosynthesis can still occur. Macro algae can be harvested weekly from the outer margins that house the older (nutrient-rich) growth. The refugium has a rubble rock (1-2") substrate in the newer design. I found that the plastic mesh wouldn't allow detritus to settle to the lower benthic zone where it could be broken down by benthic (bottom dwelling) invertebrates such as serpulid and fan worms, tunicates (squirts), sponges, and zooplankton. Rubble rock provides a good surface for gracilaria to grow. It's also the perfect media for fostering the growth of zooplankton such as copepods, anthropods, isopods, and mysid shrimp.
The lower level of our Duplex is the benthic zone. This area houses the small invertebrates that populate all well established sumps. They occur here under natural conditions, those being diffused light, reduced flow, a nutrient source (phosphate, nitrate, silicate, bacteria, excess heavy metals/trace elements), and a viable media to attach to, and grow from. I found the limiting factor to be insufficient surface area to populate.
Live rock will provide more surface are than a bare sump, but an eggcrate grid is the best. It provides 360 degree living quarters with no flow restriction. Encrusting tunicates and clusters of feather dusters climb the eggcrate like a lattice. Tunicates or sea squirts, have been well documented as water polishers, with no significant toxins (allelopathy). Sponges on the the hand are great water polishers but considerably toxic. As a quick note, many people mistake tunicates as sponges. The rule of thumb for identification is, tunicates have "mouths" that open and close, while sponges have pores.
Reef aquariums are rich with benthic invertebrates, but they don't fare well in high flow and intense lighting. Steve Tyree has experimented with dark ("cryptic zones") within the aquarium to foster their growth, but it doesn't mesh well with popular aesthetics, and surface area is still a limiting factor. The more you do to encourage the growth of benthic invertebrates in the display tank, the worse the conditions become for fish and corals.
Jaulberts' plennums were a scaled down version of my benthic zone. While Jaulbert believed his plennums to be successful due to a passive water exchange, they're measure of success could be due to their suitability for water-polishing benthic invertebrates. This would explain why some plennums worked, while more anoxic, or less populated versions didn't.
Leng Sy believes that the key to his system is the bioavailabilty of trace elements in his Magic/Miracle/Mineral Mud. This is an easy assumption to make if you believe that captive reefs are trace element/heavy metal-poor. If you look at Dr. Ron Shimeks' work
http://reefkeeping.com/issues/2002-1...ure/index.php, it's pretty clear that we're working with a surplus not a deficit. The mud is a reasonably good media for benthic invertebrates to grow, and likely the cause of sporadic success with these systems. Of course, it's easy for Leng Sy to put his faith in the marketable aspects of his design (Mud), rather than the methodology itself. With the high cost of facial mud treatments, I can't blame him.
The final zone of the Duplex sump is an area for chemical media, heaters, and the return pump intake. An UV sterilizer on the return, or a bypass line, is a useful tool in the control of aiptasia. The UV unit will not kill larger organisms like zooplankton, but it will kill smaller pathogens like aiptasia, bacteria and parasites.
It takes 6-9 months to develop a decent population of benthic invertebrates in the Duplex System. Using live rubble rock helps this process along.
It's too new of a system for me to truly measure its' value, but the substantial population of benthic invertebrates that make their home in our sumps are consuming something. It's a fair assumption that their nutrient source is the stuff we're trying to get rid of. A greater biodiveresity and well rounded ecosystem is clearly the key to replicating natures balance.
I'm looking forward to hearing of your experiences using this method.