Cryptic Zone Dixcussion

[spanko]

There is a thread in the Nano tank section where Rotary and I hijacked a users thread and started a short discussion on the subject above. I said I would post some info from an article about them here in this forum to see if others were interested in talking about it or maybe showing some of their own "experimentation" with a cryptic zone filtering system.
Here we go:
Quoted from Practical FishkeepingSteve in the article is Steve Tyree Steve has been farming and distributing captive stony corals since 1993.)
Exploring the zones
Steve is a thinking man's reefkeeper. Most of us are content to enjoy observing the day-to-day happenings in our reef tanks and admire the many new forms of life that spring from the live rock, turning tiny crevices and the undersides of this vibrant living material into brightly coloured sponges, tunicates and tiny fan worm colonies. But not Steve. He is happier pondering the reasons for these explosions of life.
Early in his research, Steve discovered a scientific term "the gradient concept", which describes how marine life forms can be graded by the amount of light they receive to allow them to be categorised into different light zones. He decided to apply the same principles and come up with a series of zones that could be applied to reef aquariums.
"Traditionally," Steve explained, "scientists use three main physical parameters - light, water current and the type and amount of particulate matter suspended in the water column when describing the environmental conditions of the various natural tropical reef zones they have identified.
"The most commonly used zonal categories are defined as the Exposed and Semi-Exposed Zones. The Exposed Zone is described as a shallow water environment, which receives strong sunlight in the range of 10-100% of the light applying on the surface of tropical reef waters. These conditions are identical to light levels found on a shallow reef platform, where many of the light-requiring photosynthetic stony corals occur, and are representative of the conditions we try to attain in our stony coral captive reef systems.
"The water currents typical of this zone are in the order of 10-50cm per second, but can occur up to as high as 150cm per second. Organisms living in this zone need to have strong, dense structures to withstand such strong currents.
"Due to the strong water movement, large amounts of suspended particulate matter can also be found, but the over-powerful currents often prevent normal suspension feeding by filter feeding organisms from occurring.
"The Semi-exposed Zone is categorized in a similar manner, but light levels are lower, more in the order of 5-10% of the levels occurring at the surface. Water currents in these semi-exposed conditions range from 1-10cm per second, so organisms still require strong, dense structures to survive.
"Particulate matter remains suspended in the water column and allows passive filter-feeding organisms, like soft and hard corals, that can consume large to small particulates, to thrive.�" Continued

 

[spanko]

"(Passive filter feeders are organisms that trap passing particulates by pumping water through their bodies.)
"The overall conditions in this zone are typical of lagoon reefs, back reef and deep reef conditions, and while the only photosynthetic organisms found are those that can tolerate low light conditions, a wide range of non-photosynthetic life forms can easily survive. Again, the conditions in this zone can be applied to captive reef systems and will be recognized by reef aquarists who operate deep tanks or employ lower than optimal light levels.�
While Steve recognizes each of these classic natural reef zone categories in his own system, he was aware that there were other equally important zones that could be relevant to reef aquarium keeping that needed to be considered.
He finally came up with three more zones he regarded as principal elements for his own zonal-based reef modeling theory.
His first was defined as Semi-Cryptic and occurs in the deep lower sections of natural reefs or in reef areas with overhangs in shallow water. The main defining characteristics are very low light levels which would only support photosynthetic organisms that can survive in minimal light conditions.
The second is Cryptic and applies to the oft-called "twilight" zone of a reef, deep within caves or beneath the reef platform in shallow water. Incidental light is far too weak to support photosynthetic life forms.
Steve's third and final zone was the Filter Feeder Zone, a combination of the semi-cryptic and semi-exposed zones. The main feature is continuous water currents strong enough to keep medium to large particulate matter in suspension and available for filter feeding organisms.
In nature, this is the realm of gorgonian and non-photosynthetic soft corals. It is currently one of the biggest challenges to reefkeepers.
Back to basics
In order for there to be a clear understanding of these proposed new zones, Steve decided it was necessary to define what he meant by "cryptic".
He referred to biological dictionary terminology, which defines cryptic as an adjective referring to "organisms belonging to enclosed places and those organisms with a hidden mode of life". Good examples of these organisms can be found in a wide range of animal classes including corals, sponges, ascidians, hydroids, crustacea, mollusks and many more including whole families of fishes that live reclusive life styles.
Steve's three new zones needed to be defined in terms of the main parameters. He describes the Semi-Cryptic Zone as having light levels between 1% and 5% of those at surface level, with water currents in the order of 0.1-1cm per second, which allows only fine particulate matter to remain in suspension because of the weak water movement. Typically both passive and active suspension feeders are the major colonizers in this zone.
The Cryptic Zone has less than 1% of the light at surface level with currents less than 0.1cm per second. Only very fine particulate matter are suspended in the weak currents, and organisms develop very delicate structures and are dominated by active suspension feeders that generate currents through their feeding mechanisms.
Light has not a critical role to play in the Filter Feeder Zone and could vary 1-10% of the light levels on the surface. Similarly, a wide range of currents also could apply ranging from 1-10cm per second. The water would contain large amounts of suspended particulate matter and passive filter feeding organisms would thrive in these conditions."
Continued

 

[spanko]

"Putting into practice
One of the main objectives was to see how this could be applied in a fresh approach to reef aquarium filtration which would use various types of cryptic organisms as a natural filtration process.
His first attempt involved a tri-zonal method of approach based on dividing a reef tank into three distinct zones arranged side by side. To the left of the tank was an exposed zone, which was the main viewing area and featured strong to low light intensity to support a wide range of photosynthetic organisms. Water currents varied from strong to low and contained large to medium particulate matter in suspension.
A filter feeder zone was located beside the exposed zone without any other form of physical barrier other than the sloping mound of live rock, which reached almost to the surface, to form a filter feeding channel.
No specific lighting was installed, and water pumped from the exposed zone provided a low to weak current. The water contained a wide variety of different-sized particulate matter.
Between the filter feeding zone and the next zone, Steve installed a black acrylic diffusion screen drilled with lots of holes of 3/16" diameter. This formed a cryptic zone where water from the filter feeder zone diffused through the screen, admitting only very fine grades of particulate matter.
Almost no light was admitted to this area, and all of the organisms were heterotrophic (requiring a supply of organic material, ie food, from the environment). As there was no plumbing in this area, water movement was minimal but the natural filtering effect was similar to that of a protein skimmer.
Steve�s next design employed a ⌦bi-zonal method with an acrylic diffusion screen dividing the tank into an exposed zone at the front with a cryptic zone behind.
As with the earlier approach, strong to low lighting was arranged at the exposed side, but precluded from the cryptic. Although designed on a two-zone basis, it should be recognized that semi-exposed reef conditions would also apply under and in-between the live rock.
Encouraged by his success with each of these methods, Steve decided to explore the commercial possibilities and designed a hybrid zonal method for use in his coral culturing business.
A series of coral frag-holding tanks, which we could call the Exposed Zone, were connected to three fully populated cryptic zone tanks with a compartment in-between containing two large 200-micron filter bags.
Water passed from the holding tanks through the mechanical filters and then into the cryptic tanks from where it passed through a protein skimmer before returning to the holding tanks. Steve was successful with thriving populations of cryptic organisms in the Cryptic Zone and good, healthy growths of frags in the holding tanks.
The organisms in his Cryptic Zone filters are varied, but sponges usually contribute the most in bioload terms. Sponge growth is quite remarkable, but as it can be harvested in a similar way to the caulerpas in an algae refugium as a means of exporting nutrients, large sponge populations are not a limitation.
Other organisms in the Cryptic Zone include sea squirts, bivalve mollusks, feather duster worms and foramiferans. Cryptic reef plankton also occurs, but it has been difficult to maintain pelagic plankton in captivity due, it has been theorized, to the pumps used to move water and generate currents damaging these delicate organisms.
Reef plankton differs from oceanic plankton in compromising two or three species of copepod.
Examples of the organisms used in Steve�s filter feeder zone filters include calcareous sponges, non-hermatypic corals, ascidians (Botryllus sp), thorny oysters and other bivalves and foramiferans.
As many of these are very decorative, there is no reason why the filter feeding zone could not form part of the viewing area of the tank.
Steve says most of the systems he�s designed and built have been for research or for production-based systems. He is looking forward to the next stage, designing and building marketable show tanks.
New designs are also in the pipeline for a Quad Zone system employing two diffusion screens, one with large holes, and a further screen with much smaller holes.
All of Steve�s methods have succeeded magnificently in terms of the health and growth of show tanks subjects such as coral and cryptic organisms like sponges and tunicates, and he is now looking towards captive spawning a whole range of cryptic organisms.
He is also hoping to push aside the barriers to keeping non-photosynthetic soft corals like the Dendronephthya species.
This article was first published in the Christmas 2004 issue of Practical Fishkeeping magazine."
In the words of CFR.............................discuss

 

[subielover]

Very interesting read spanko. It would certainly makes refugiums cheaper as there would be no needs for any lighting system.