Over the years, the methods of filtering reef aquariums have been subject to deep debates over which way is best - and the degree of technical sophistication needed to maintain a successful reef tank.
The overall trend has been towards a less high tech/more natural approach using methods like the Berlin system, Jaubert's 'Microcean' water purification process based on the plenum filter and, most recently, Sy's Ecosystem filter, which uses an algal filter with a non-calcareous media called 'Miracle Mud'. Whatever your views on these, the huge success over the past ten years in keeping delicate corals and other reef subjects is mainly due to the superior quality of water purification such natural methods of filtration can offer.
This month, I am reviewing a plenum-filtered aquarium, on Jaubert's home ground, where most of the research into plenums has taken place. This famous reef tank at Monaco Aquarium was one of the first plenum-filtered systems to receive world-wide acclaim.
Professor Jean Jaubert of Nice University first perfected the living sand method of enhanced biological filtration, a process that received a French patent in the late 80's followed by a US patent in 1991. Jaubert's method became known as the 'Microcean' process. It simply required a layer of sand substrate to be sandwiched between the main water of the tank and a water filled void, called a plenum, beneath.
The importance of this new method became evident in 1989 when Jaubert worked with the Monaco Aquarium (within the Musée Oceanographique of Monaco) in transferring a complete live coral reef from Djibouti in the Red Sea. With the help of technicians, he carefully installed the reef in a 40,000 l./8800 gal. tank at the museum.
The Microcean water purification process received its first large-scale trials with this system. It was soon successfully maintaining a fully reconstructed reef environment, complete with all the flora and fauna of a natural reef including continuously growing corals.
This major success led to the construction of a series of new tropical marine tanks in the Aquarium, each with reconstructed reefs of living coral, the exhibits featuring the Indian and Pacific Oceans, Red Sea and the Caribbean.
The high esteem in which the Monaco Aquarium is held rests firmly on these exhibits, which thrive thanks to Jaubert's Microcean process and the expertise of the technicians and biologists of the aquarium.
I've chosen one of the smaller exhibits from the Tropical Hall of the museum for my review as it compares most easily with the other hobbyist tanks looked at in this series. This particular tank was featured widely in the hobbyist press due to its unparalleled success and played a pivotal role in making hobbyists aware of the success of the combination of Jaubert's Microcean water purification methodology and the expertise developed at the aquarium into the culture of reef building corals.
Pierre Gilles, deputy head of the Aquarium, has an intimate knowledge and experience of all tanks exhibited in the Tropical Hall and agreed to provide all the vital statistics for the tank. While the success of all of the tanks in the temperate exhibits relies on semi-closed or open circuit filtration with permanent renewal using seawater extracted from the sea below the museum, all the tropical tanks operate on a totally closed circuit basis.
The tropical exhibits are therefore managed either separately or in connected small groups. The physical and chemical parameters of each tank and its technical equipment is monitored 24-hours-a-day by a computerised management system.
Under the spotlight
The tank I'm reviewing (C9) belongs to a small series of connected reef tanks (C4 through to C14). The tanks were set up in 1992 to exhibit Red Sea subjects. The Aquarium was already displaying a number of live coral tanks, including the Djibouti exhibit, and the technicians and biologists had perfected methods of coralliculture, which provided large numbers of new coral colonies for this series of exhibits.
Each of the exhibits was to recreate different parts of a complete living coral reef and display animals from each of the distinct habitats with which they are associated. This allows animals that would not live peaceably together to be separated and in their own precise environmental conditions, yet because they all live in the same water mass, all participate to the balance of the system.
Pierre points out that due to the volume of the whole installation (more than 5m3/17'3 including sumps) water management is easier and the parameters are kept steady over long periods.
Ten years later, this series of exhibits is functioning well. C9 is the largest tank with a volume of 2378 l./523 gal. and is 164 x 125 x 116cm (65" x 50" x 46"). The hard corals (mostly Stylophora pistillata) have grown very large - two colonies became so big that the bottom of the tank and other colonies became shaded. In 1996, they were removed; the smaller colony (weighing more than 20kg/44lb) was lifted out in one piece but the other needed to be cut into sections for removal. A researcher from the Centre Scientifique de Monaco (Manuel Marchioretti) found that frags from these colonies showed an impressive growth rate of 1% (dry weight) per day. The net calcification per m2 per year was the same as one measured in healthy coral reefs (up to 10kg Ca CO3 per m2 per year in the best conditions).
A colony of Brain coral, Lobophyllia hemprichi, introduced to the tank in 1993 when it was 20cm in diameter, is now nearly four times that size.
Growth of Acropora spp. is equally impressive and as space is limited and the growth rate still very high, branches and parts of colonies are frequently harvested from the tank for the Aquarium's coral culture facility.
It's quite difficult to find a single cm2 of hard substrate that hasn't been colonised by stony corals; even the glass side panels of the tank are covered with other colony-forming invertebrates such as corallimopharians, and colonies of Parazoanthus and Xenia soft corals.
As Pierre and I admire C9, I am amazed at the mature, natural reef-look of the display. Slow-growing corals, like the Brain coral, look every bit as established as faster colonisers like the Acropora and Stylophora species.
The unusual shape of the tank, which is quite deep for its length and width, allows for a fresh approach with the aquascaping. Most of the corals are arranged on the side walls of the tank, reaching up from the substrate to the surface giving a gorge-like effect with vertical walls. There is no mistaking the type of Red Sea habitat this represents - similar vistas occur commonly on the vertical drop-offs of Ras Muhammed on the Egyptian Red Sea, where vertical underwater cliffs cleaved by numerous faults plunge downwards for several hundred metres.
The choice of fish, of Red Sea and Western Indian Ocean origin, also add to the illusion. Fairy basslets, Pseudanthias squamipinnis, instantly conjure up reefscapes that anyone lucky enough to have dived the Egyptian Red Sea would recognise. Red Sea basslet, Pseudochromis fridmani, and Midas blennies, Ecsenius midas, are also typical inhabitants of this type of vertical cliff habitat.
The extent to which this tank resembles the natural environment is marked by a remarkable feature of the exhibit: a pair of Red Sea pipefishes, Corythoichthys schultzi, which have lived in the tank for more than seven years. These fish have never been fed but hunt the small copepods that swarm in the crevices of the rockwork. They have bred several times -the male can often be seen with eggs in his ventral pouch.
Myriads of small invertebrates have adopted the various micro habitats, from the deepest layers of the substrate up to the rocks and Caulerpa beds - even within the corals (Trapeza crabs). The amazing micro fauna includes crustaceans, molluscs, echinoderms and annelids.
In Coral Reefs, published in 1989, I said:
"It is easy to understand how, in the enclosed system of a home aquarium, it is difficult to simulate the exacting requirements of many coral reef fishes and invertebrates... It seems inadvisable to take them from their natural environment in the first place and in the interests of conserving these animals and the beautiful reefs they build, it would be only right not to encourage their collection for the hobbyist market."
If I had known at that time that Jaubert and the expert coral culturists of the Monaco Aquarium were making such startling breakthroughs both in keeping and propagating stony corals and other delicate reef inverts, I'd have been pleased to eat my words!
The pioneering work conducted by Jaubert and other experts in the field of natural forms of reef aquarium filtration and coral propagation have brought about the improvements we have seen in culturing delicate reef subjects. C9 symbolises these developments. I find the combination of Jaubert's creative natural filtration and the refugium-complete food web approach quite inspirational. I've no doubt this aquarium remains at the cutting edge of development in closed circuit reef aquarium design.
I would like to thank Pierre Gilles and the members of his team, Fran Otero, Sophie Pigno, Jean-Marc Jacquet and Gilles Perez, for their help.
Pierre's feeding tips
All the tanks in the Tropical Hall are treated individually as regards feeding but as they all share the same water there is an element of interplay, one tank to the other, with any fine feeding material suspended in the water column. The routine for C9 is:
# Daily feeds of live brine shrimp.
# Daily feeds of finely chopped frozen clams, shrimp, fish and cuttlefish
# Monthly feeds of vitamins including stabilised Vitamin C added to frozen food 20 minutes before feeding.
Aquarium vital statistics
C9 is one of a series of tropical reef tanks served by centralised Jaubert's method sand bed filters. It measures 164 x 125 x 116cm (65" x 50" x 46"). The capacity of this particular tank is 2378 l./523 gal. but the whole system contains more than 5000 l./1098 gal. including the sumps.
C9 and the other tanks in the series are connected to two remote Jaubert sand bed filters with a total capacity of approx. 9.25m3/40 sqft and each bed is 20cm deep. Each of the display tanks are fitted with Jaubert sand beds as the substrate to each aquarium, so the total size of filtration sand bed available to the series of tanks including these beds is around 13.82m3/46 sqft.
The living rock in each display tank also contributes to the biological filtration capacity. C9 contains approx. 4.25m3/14ft3 and the 11 tanks have in total 5.75m3/19 ft3. A traditional mechanical sand filter is also employed containing 75kg/165lb of pure silica sand.
Thanks to this combination of filtration methods the water is clear and cleansed of nitrogenous wastes with very little damage to any larvae, eggs and plankton produced within the system. The mechanical sand filter does eliminate some of these elements but each tank is acting as a refugium on a constant basis and the design allows for mechanical filtration to be avoided and a true food web to be created.
Activated carbon is used to cleanse the raw sea water extracted directly from the sea below the aquarium. This water renews the water in the whole series of tanks at a rate of 250 lph/55 gph equivalent to a 5% per hour water change of the total water holding capacity of the system.
In terms of C90 this means that around 40 l./9 gal. of the tank contents is replaced every hour with natural seawater.
Due to weather conditions and various other curbs on running this system, water changes are not conducted on a full 24-hour or a complete annual cycle.
The quality of the water in this series demonstrates that the Jaubert system, in combination with regular water changes, is capable of supporting complete mineralisation, nitrification and denitrification processes without the need of protein skimming.
Powerful protein skimming has the disadvantage of stripping the water of various elements such as plankton-based material, together with important nutrients like iodine and trace elements essential for the balance of a coral reef aquarium. It would seem that the advantages gained from the refugium true food web approach used for this series of tanks considerably outweigh the disadvantages of not using powerful skimming action.
Using natural seawater with regular water changes adequately replenishes and maintains calcium/carbonate levels, allowing the stony corals within the system to function in growth terms at levels similar to those on natural reefs. No additions of these elements are made and the stability of the water parameters remains constant.
With the water movement in tank C9 being a combination of filter circulation of the whole series of tanks, plus pumps devoted to tank water circulation and movement in of raw sea water/draining away of surplus, circulation is difficult to assess precisely. A rough assessment would suggest that C9 receives 8000 lph/1760 gph through filter circulation, plus 2000 lph/440 gph tank circulation and 40 lph/9 gph new sea water per hour: a total of 10,030 lph/2209 gph.
Pierre considers the lighting the main key to the success of C9. This is a combination of metal halides and fluorescent tubes as follows:-
# 2 x 1000w 6500K Osram HQI
# 2 x 36x Osram Fluorescent Tubes Tld Blue.
The intensity of the light is regularly monitored using a photometer equipped with a hemispheric probe. The light intensity usually ranges from 250 to 800 or more microeinsteins/m2. Most of the coral colonies in the tank receive between 300-500 me/m2.
The metal halides are replaced once every year changing one bulb at a time with a six-month gap in between to avoid a sudden increase of intensity that would be harmful for the corals.
Each of the metal halides is adjustable in height from the water of between 18-71cm. By measuring the light intensity at 20 specific points in the aquarium corresponding to various coral colonies, it is possible after replacing bulbs to adjust the l amps in order to obtain the required intensity. Lamps are then slowly lowered as the intensity decreases with time.
The fluorescent tubes have a novel use. The structure of the tank is mainly of beige resin with a window at the front through which the aquarium is viewed and a glass back panel faced with blue opaque acrylic. The two fluorescent lights are mounted vertically against this acrylic back panel to create a blue light in the aquarium and the illusion of deep blue water. Though no research has been done on the subject, Pierre believes that the blue colour could possibly trigger the metabolism of the corals. In any event, the blue colour undoubtedly highlights the colours of the fish and the corals.
# 2 x 1000w HQI
# 2 x 36w fluorescent = 2072w
# Surface area: 2.05m
# Light intensity: 1011w/m2
# Light on: 07.30
# Lights off: 21.30
# Total: 14 hours per day
Temperature control is achieved by fan cooling the whole air space of the Tropical Hall.
Practical Fishkeeping - Issue 8/August 2002