New Trends in Reef Keeping: Is it Time for Another Change?
by Julian Sprung B.Sc. and J. Charles Delbeek M.Sc.

Approximately four years ago George Smit began a series of articles in
which he asked if it was time for a change in our philosophy of
keeping marine aquariums (Smit, 1986). What followed is, of course,
part of marine aquarium keeping history as the concept of miniature
reef aquariums caught on quickly and spawned a healthy and vigorous
industry. In this article we would like to discuss the possibility
that perhaps it is again time for a change in our thinking towards
marine aquariums. Although commercial names are mentioned in this
article, they were included only for the sake of completeness
and accuracy, not as any form of endorsement. This article is merely
intended to bring to North America, some of the ideas and philosophies
that are being practiced by advanced hobbyists and professionals in
Europe today. Ultimately the decision to try the techniques described
in this article, lies with you, the hobbyist, we are only offering you
the opportunity to explore this philosophy.

The heart of most reef aquariums today is the trickle filter. However,
as we hope to show in this article, excellent success can be attained
with alternative forms of filtration, and in one case, no filtration.
While we in North America have been busily trying to catch-up to the
Europeans in reef system technology, they have not been sitting idle.
Perhaps we have only seen one side of the European marine aquarium
hobby. We hope to be able to show you another, somewhat different
philosophy. Through numerous articles in European literature, personal
communications with European hobbyists and reports from hobbyists who
have recently returned from Europe, we have gathered information on
hobbyist and professional systems located in Germany, France and
Norway.

The Methods
Many reef systems in Europe are no longer running on trickle filters
or any type of external biological filtration, as we know it. The
majority of systems rely solely on foam fractionators (protein
skimmers), live rock and in some cases granular activated carbon
(GAC), for filtration. It was not until they removed trickle filters
from their aquariums, that many European hobbyists felt that they
began to experience long term success (Nilsen, 1989; Stüber, personal
communication 1990). There are in fact 4 main factors that these
hobbyists attribute their success to: 1) the use of foam
fractionators, 2) the use of live rock, 3) halogen quartz iodide
lighting, specifically the Osram HQI(Registered) TS 250 W/D, 5200K
lamp and 4) the regular use of a saturated calcium hydroxide solution,
also known as kalkwasser (although not all aquarists use this
solution, as we shall see later).

Protein Skimmers
Foam fractionators have replaced the trickle filter as the filtration
method of choice in many reef aquariums. Water is fed directly to the
skimmer via a combination of overflows and/or subsurface intakes
combined into a prefilter/sump. From there the water is pumped into
the skimmer and allowed to return directly to the tank. The majority
of the water movement is achieved by circulation pumps in the main
tank and return lines from the sump. The prevailing attitude appears
to be that one cannot overskim a tank and 2 to 4 skimmers connected in
series is the norm for tanks from 100-1000 gallons (Molder, 1990;
Nilsen, 1990, personal communication). These skimmers can range in
height from 3 to 6 feet. For example, skimmers are used as the sole
form of filtration at some public aquariums in Europe such as the
Bochumer Tierpark in Bochum, Germany which has a beautiful 4 000 L
coral/fish aquarium filtered by a battery of 6 foot skimmers. Stüber
(1990, personal communication) states that experience has shown that a
flow rate of 1 L/hr of air per litre of aquarium water is sufficient
to allow a proper CO2 concentration and adequate skimming.

Ozone is generally not used in these systems although small amounts
(i.e. < 5 mg/hr) can be used to increase the efficiency of the
skimmer, to oxidize yellowing compounds in the water or in case of
emergencies such as disease or microalgae outbreaks.

The Importance of Live Rock
Many of you are probably wondering where biological filtration will
take place if there is no trickle filter. The answer lies in the live
rock. The use of live rock as a biological filter medium within the
aquarium, allows for the establishment of natural biologic processes
such as occur on the reef. These processes will become established
whenever significant quantities of live rock are used, whether a
wet/dry filter is used or not. However, a wet/dry filter can affect
the efficiency of these processes.

Live rock contains a multitude of bacteria both on the exterior and
interior of the rock, some of which are the exact same as those found
in a seeded wet/dry filter. Hence, they are perfectly capable of
nitrification. When a fish passes ammonia across its gills into the
surrounding water, or defecates, these products do not simply seek the
wet/dry filter underneath the aquarium. They are, instead,
competitively utilized by whichever organisms come in contact with
them first and considering the high velocity flow recommended in a
reef aquarium, these are usually the rock, algae and invertebrates.
Algae growing on the live rock as well as various zooxanthellae
containing invertebrates (hermatypic), will rapidly take-up dissolved
ammonia. In addition, various heterotrophic bacteria in the system
will rapidly breakdown solid wastes and numerous invertebrates will
ingest solids such as feces. In turn, if ammonia is excreted by these
organisms, it may be rapidly consumed by algae and hermatypic
invertebrates situated on the rock.

The key word here is proximity. The nitrifying bacteria, even on the
rocks, are in for serious competition for nitrogenous waste. Still,
they do get some and, like their counterparts in the wet/dry filter,
they convert ammonia to nitrite, and nitrite to nitrate while
consuming oxygen. However, unlike a wet/dry filter, the nitrifying
bacteria on the rock are in very close proximity to anaerobic areas
within the rock. For this reason, the little bit of nitrate produced
at any given time can be immediately denitrified by facultative
anaerobes in the core of the rock, where there may be plenty of
organic material to allow the process to occur completely and
efficiently. In addition, algae and corals growing on the surface of
the rock can also use the nitrate in the small pulses they are
accustomed to using. However, if the level of nitrate in the water is
too high, the system becomes saturated and these natural processes do
not function efficiently. In this situation the algae and
zooxanthellae cannot use their nitrate utilization mechanisms to pull
the nitrate level down. Still, high levels of nitrate in the water,
combined with high water flow, can create a situation where incomplete
denitrification can occur which would tend to stimulate algae growth
on the rocks; desirable or undesirable. In this situation the wet/dry
filter functions as a nitrate factory. The presence of live rock can,
however, inhibit wet/dry nitrate production either partially or
completely, depending on the bioload (animals and feeding) in the
system.

Original designs for wet/dry filters incorporated large wet sections
filled with gravel. These contained anaerobic zones which functioned
somewhat like live rock because of the proximity to the aerobic
nitrification, but were a drag on the oxygen content of the water as
they became progressively clogged with bacterial detritus and soon
became nutrient sinks which could stimulate undesirable algae growth.
These wet beds clogged and needed periodic cleaning, even when good
prefiltration was employed, since the bacteria in the dry and wet
sections continuously sloughed off a refractory organic detritus. For
this reason, recent wet/dry filter designs have smaller wet sections,
typically with easy to service media such as foam cartridges. If the
wet section can become a nutrient sink, then it follows that the live
rock could do so too, and in fact they do. However, the rocks are not
in a position where they act as a continuous mechanical filter, as the
media in the wet section is, so they do not clog. On the contrary,
numerous boring organisms within the rock continually spew forth
detritus loaded with nutrients which should be removed periodically
from the system, either by siphoning or via the prefilter.

Bearing all this in mind, a reef aquarium can operate beautifully with
or without a wet/dry filter but there are many variables that can
affect the level of success achieved. Above all, limiting the sources
and storage zones for nutrients is a general means of keeping the
system operating properly whether a wet/dry filter is used or not. One
can see, for instance, how important a piece of equipment a protein
skimmer really is as a complement to the wet/dry filter. In removing
nitrogen rich compounds before they are broken down, the protein
skimmer lowers the wet/dry filter's potential production of nitrate.
It's value is not lost in systems without a wet/dry filter either.
This is why most hobbyists running their aquaria with skimmers only,
consider skimming an essential element for long term water quality.

Lighting Systems
The lighting system of choice in some countries in Europe now seems to
be HQI(R) lighting, specifically the lamp mentioned above for smaller
tanks and 400 W 5600 K HQI(R) Osram D lamps for larger (>500 gallons)
systems. The lamps mentioned above are double ended, however, there is
also a single ended lamp, the Osram HQI(R) T 250 W/D 5400 K which can
be used in screw-in type (mogul) metal halide fixtures. There are
other bulbs available of course and the hobbyist is urged to explore
other manufacturer's lamp models. As long as the colour temperature is
over 5200 K and the colour rendition index (CRI) is over 90, they may
be suitable as well. One problem with HQI(R) lighting though, that in
our opinion has not been stressed enough to hobbyists, is that
although they will maintain their intensity for up to 4 years, their
spectrum changes drastically in as little as 1 year, in some cases as
much as 1000 K (Stüber, personal communication 1990; Osram
specification sheet; see Delbeek, 1990 for a more in-depth discussion
of metal halide and fluorescent lighting). Therefore, these lamps are
replaced on a regular basis, approximately once/year or more
frequently, depending on the organisms kept.  It is interesting to
note, however, that the use of supplemental blue fluorescent lighting
is becoming increasingly common, especially Actinic 03, Thorn EMI Blue
or Lumilux lamps.

Essential Elements
The use of a saturated calcium hydroxide solution has gained little
widespread use in North America although some authors have mentioned
its use in recent publications (Delbeek, 1990; Sprung, 1990; Thiel
1988). The main purpose of the regular use of this solution is to
maintain the calcium ion level of the aquarium water above 420 mg/L,
to promote the growth of coral, coralline algae and calcareous algae
such as Halimeda. The solution is prepared quite easily, however, one
must always be mindful of the proper handling of any chemical and
avoid direct exposure/contact with the powder. Calcium hydroxide is
available in various levels of purity from chemical supply companies
and, perhaps, druggists. To make a saturated solution of calcium
hydroxide the powder is dissolved into freshwater (preferably reverse
osmosis, deionized or distilled) at room temperature, at a
concentration of 3 g/L e.g. add 12 g calcium hydroxide to 4 litres of
freshwater (Stüber, 1990, personal communication). Although the
solubility of calcium hydroxide is 1.5 g/L at room temperature, by
using 3 g/L you are sure to achieve a saturated solution and the
solution can be reused. Make sure the container has very little air in
it as the carbon dioxide in the air will combine with the calcium ions
in solution and precipitate them out as calcium carbonate which is
something you want to avoid. This is easily detectable as the solution
will become milky-white in colour. After adding the powder to the
water, cover the container tightly and mix the contents. Allow this
solution to stand until settled, usually 12 hours. After settling,
decant the clear fluid carefully into another container and you now
have a ready to use solution. The first container can now be refilled
and the process repeated using the undissolved powder remaining at the
bottom of the container. Handle the solution carefully as it is
caustic, with a pH of 12! The clear solution is added directly to the
tank to replace water lost due to evaporation by slowly adding the
water either via a dosing pump or float valve over a period of several
hours. Do not add this solution all at once as the resulting pH
increase can seriously affect the inhabitants. If you plan on using
this solution check your pH and carbonate hardness (alkalinity)
frequently to make sure they are not adversely affected by the calcium
hydroxide solution additions. One of us (J.C. Delbeek) has been using
this solution for over 4 months now in a 30 gallon system, with
absolutely no change in pH and only a slight drop in KH. Coralline
algae growth has increased noticeably over this period. Please note
that if you are not having any problems maintaining the calcium
concentration over 420 mg/L (perhaps you are using tap or well water
that already has high levels of calcium and magnesium), your pH
fluctuates very little from day to night, your KH does not drop and/or
your calcium bearing organisms are flourishing, then you may not need
to add this solution. However, many hobbyists in Europe now use it
extensively. An alternative to calcium hydroxide is calcium chloride.
A number of American hobbyists, are using calcium chloride with
excellent success too (e.g. J. Burleson; M. Paletta and J. Sprung,
personal communications, 1990). However, caution should be exercised
when using this solution as one can easily raise calcium levels in the
tank to much higher levels. Calcium chloride has the added benefit of
having a neutral pH. Calcium chloride is useful also in initially
raising the calcium level to the desired concentration in the tank;
this level can then be maintained using the calcium hydroxide solution
as described above. In any event, always use a calcium test kit to
monitor your aquarium before and after dosing the aquarium.

Another element that is required in trace amounts by calcareous
organisms, especially coralline algae and hard corals, is strontium.
This is added to the aquarium by making a 10% solution of strontium
chloride (e.g. 100 grams per 1000 mL distilled water) which is slowly
added once a week at the rate of 1 mL per 150 L of aquarium water
(Stüber, personal communication, 1990). An alternative would be to use
a dosing pump to add the solution over a weekly period. Again exercise
caution in handling this chemical and add it slowly to the tank. Some
European hobbyists add this supplement, some do not.

The Systems
The first system we would like to describe belongs to Mr. D. Stüber of
Berlin, Germany. Mr. Stüber has been in the hobby for over 20 years
and his system is representative of the so called "Berlin School" of
aquarium keeping. Two 250 W HQI(R) metal halide lights (replaced every
six months), supplemented with blue fluorescents (Actinic-type bulbs),
are used on his 700 L aquarium. The lights come on and go off in
stages over a 13 hour period. From 10.00 to 12.00 only blue
fluorescents are on; at 12.00 one HQI light comes on and at 12.30 the
second. At 21.30 the first HQI(R) goes off and at 21.40 the second.
The blue fluorescents go off at 23.00 then two small 8 W incandescent
bulbs come on and go off again at 23.30 (Stüber, 1989). Filtration
consists simply of a small overflow which drains into a sump. The sump
contains a few small compartments for prefiltration and one for
calcareous gravel in which denitrification is believed to occur. Water
is pumped from the sump into 2 four foot, air-driven skimmers
(completely cleaned everyday) from where it flows back into the tank.
These skimmers were designed and built by hobbyists in Berlin and have
been used for many years. Air is pumped into the skimmers such that a
total of 700 L/Hr of air enters the skimmer which is approximately one
litre/hour of air per litre of aquarium water. There are 6 Tunze
Turbelle water pumps located in the tank itself to promote vigorous
water movement (Stüber, 1989).

There are basically two types of aquariums kept in Berlin; soft coral
tanks and hard coral tanks; fish are more an afterthought. Water
chemistry is of utmost importance in both types of systems. Mr.
Stüber's water chemistry parameters are as follows: pH 8.3, nitrate
less than 10 mg/L, nitrite 0.05, KH 8, temperature 26oC and specific
gravity 1.025 (Stüber, 1989). Somewhat surprising perhaps, is the
redox which varies between 180 and 195 mV as measured with a silver
calomel probe. However, it is very difficult to compare redox values
from one tank to the next due to innumerable variables such as probe
type and pH, so any comparisons between aquariums should be made with
caution. Ozone is not used in this system. Water changes are performed
at the rate of 5% per month. Activated carbon is used every three
weeks for a period of a few days and is then removed.

Hair algae must of course, be totally absent before any hard corals
are introduced to an aquarium. Macroalgae (e.g. Caulerpa taxifolia)
are used to help keep microalgae under control as well as numerous
snails, sea urchins, starfish (all of which help scavenge the aquarium
too) and tangs, specifically the Yellow Tang, Zebrasoma flavescens
(Stüber, personal communication, 1990).

At present the system contains over 24 specimens of hard corals
representing 11 different species. These specimens are all growing and
spreading over the rock. Mr. Stüber uses both calcium hydroxide and
strontium chloride solutions regularly in his aquarium and you can
easily see the results of these additions in the magnificent coralline
algae growth and the remarkable hard coral colonies! Species of hard
corals growing in this system include Acropora formosa (grows at the
rate of over 2 cm/year), Echinopora lamellosa, Pocillopora damicornissp.,
Porites sp., Millepora sp., Favites sp. and Pachyseris sp. (Stüber,
1989). The tank contains also Tridacna sp. clams, zoanthid colonies,
mushroom anemones, other unidentified soft corals and several fish.
The first hard coral acquired, A. formosa, was introduced into the
tank in 1983 and was about the size of a quarter. Over the years
various pieces were broken off and given to other hobbyists in Berlin.
These "daughter" colonies have grown equally well (Stüber, 1990). The
specimen of Pocillopora damicornishas been similarly distributed amongst
hobbyists in Berlin. This coral has also spawned several times with
one of the planula larva actually growing into a new colony (see
photos). One point that Mr. Stüber makes quite clear is that no other
corals, especially mushroom anemones (Discosoma sp.) and zoanthids,
should be allowed to come into contact with these hard corals as they
will sting the corals, eventually killing them (Stüber, 1990).

In Norway, Mr. A.J. Nilsen follows many of the techniques used in
Berlin in setting up systems in that country. Mainly, intense HQI(R)
lighting (replaced once/year), protein skimming, small (1%) infrequent
water changes, the extensive use of herbivores and scavengers, the
maintenance of nutrient poor water, surface skimming, exclusive use of
live rock and the addition of calcium. However, Mr. Nilsen uses GAC
continuously and replaces it every six months. Mr. Nilsen has gone
into more detail on his systems and techniques in a series of articles
in FAMA starting in August vol 13 no.7, 1990 so we will not go into
his methods any further in this article.

The next system we will examine was developed by Dr. J. Jaubert at the
University of Nice, France. This 2 m3 aquarium contains various
specimens of hard corals (Stylophora pistillata and Hydnophora exesa),
soft corals, anemones and several fish including an Asfur Angel
(Pomacanthus asfur) and a Red Sea Sailfin Tang (Zebrasoma desjardini)
collected from the Gulf of Aqaba, Jordan. The system receives 4-5
hours of direct sunlight from skylights located above the tank,
supplemented by 5 Osram HQI(R) TS 250 W/D lamps. This represents
almost 100X the amount of light the inhabitants would have received in
their natural environment (5-10 metres depth) (Jaubert and Gattuso,
1989). No external biological trickle filters, activated carbon or
foam fractionators are used on this aquarium. Circulation consists
simply of a large airstone located in one corner of the aquarium. No
water changes have been performed in the four years that this system
has been in operation.

This system employs a unique form of biological filtration (French
patent number 03 28474) within the aquarium utilizing the calcareous
substrate (coral sand and gravel) and the various micro- and
meiofaunal organisms contained within. The tank consists of a
perforated false bottom, similar to an undergravel filter plate, under
which a body of confined water exits. A thick calcareous substrate is
place on top of this plate. The oxygen content of the water above the
gravel is high while that of the water below the plate is low. This
allows aerobic nitrifying bacteria to colonize the upper layer and
heterotrophic denitrifying bacteria to exist in the lower layer
(Jaubert, 1989). Movement of all substances such as, oxygen, nitrate,
ammonium, nitrite, nitrogen and carbon dioxide through the substrate,
occurs solely by the process of diffusion (Jaubert, 1989). However,
there is a small opening in the plate at one end of the aquarium over
which the airstone is situated, which may aid somewhat in the flow of
water through the substrate.

Large organic debris is broken down by small burrowing animals in the
upper layer and their wastes are, in turn, mineralized by aerobic
bacteria. Nitrification then occurs in the upper layer and the
subsequent nitrate produced, diffuses downwards where denitrifying
bacteria convert the nitrate to atmospheric nitrogen (Jaubert, 1989).
Yellowing compounds (melanoidines) are supposedly eliminated or
neutralized by, as yet, undetermined processes (Jaubert, 1989).  Acid
secretions by bacteria in the substrate are neutralized by the
calcareous sand and the resulting input of calcium ions seems to be
adequate to keep calcium levels high enough to allow for growth of the
hard corals in the system.

Water chemistry parameters of this system were recorded over a four
year period. Nitrate levels, after an initial value of 0.350 mg/L,
dropped steadily to a level of 0.013 mg/L after four years. Ammonium
and nitrite levels remain close to 0.001 mg/L. The pH of the water
varies very little from 8.25 to 8.23. Calcium ions levels fluctuated
between a high of 520 mg/L and 480 mg/L but never feel below 460 mg/L
(Jaubert, 1989).

The success of this system is evident in the photos and growth of the
hard corals has been well documented (Jaubert and Gattuso, 1989). It
is interesting to note that Jaubert (1989) refers to the substrate in
the tank as "living sand". This is reminiscent of a term used by
Riseley (1971) in a book describing the methodology of Lee Chin Eng,
an Indonesian hobbyist who was among the first to publish reports on
the maintenance of live corals in natural system aquariums (Eng,
1961). Riseley (1971) stressed the importance of adequate lighting,
the use of live rock and, interestingly, the use of "live sand" taken
directly from the reef. Presumably this type of substrate might
contain organisms similar to those used by Dr. Jaubert in his system.
This would be an interesting project for those hobbyists who have
access to such a substrate. We would be interested in hearing from any
hobbyists who have tried such a setup or who plan on doing so. There
seems to be a great deal of room for experimentation here.

Setting-Up a Natural System Aquaria
Although we are terming these systems natural systems, they do differ
from those described by Eng (1961) and Emmens (1986) by incorporating
protein skimmers in their design. First, some precautionary notes are
necessary if we are to present this philosophy in a responsible
manner. While live rock is perfectly capable of handling the bioload
of a densely packed aquarium, this does not mean that the rock has
this capacity when you first pull it out of the shipping box after 24-
48 hours of extremely stressful conditions. Such rock needs time to
cleanse away excess nitrogenous wastes and allow for the breakdown of
various worms, algae, sponges and clams etc. on and in the rock, a
process known as "seeding" which parallels the conditioning of an
external biological filter. This brings up an interesting observation.
A sufficient mass of fouling rock will easily overcome the most
thoroughly conditioned filter, even with seeded live rock in the
system too. Two conclusions can be drawn from this observation: 1)
foul rock is real nasty stuff; 2) unless all the rock is stable (i.e.
healthy and not fouling), the aquarium will not be stable. Therefore
it should be clear that one cannot set-up a fully stocked reef tank in
one day relying on a conditioned biological filter and unseeded live
rock. However, one CAN set-up a healthy reef tank in one day using
well-seeded live rock and an unconditioned wet/dry filter as we shall
describe later.

There are several ways of creating a reef tank with skimmers and no
trickle filter but there are two main methods that we will discuss
here. One can remove a trickle filter from an already well established
reef tank or you can set-up a new tank using only protein skimmers and
no trickle filter. As all of the techniques produce the same
successful end, there is no point in suggesting a best technique. The
aquarist must decide what will be most convenient.

Removing a Trickle Filter from an Established Reef Aquarium
This category has two subdivisions, since one may either remove the
filter media from an established tank that is satisfactory in
decoration, health and has a well-functioning protein skimmer, or
completely refurbish a tank with new rock while retaining the original
fish and invertebrates, and then remove the filter at a later date.

In the first scenario, as long as the aquarium has been established
with SUFFICIENT LIVE ROCK, fish and invertebrates for at least several
months, it is perfectly safe to remove all the media from both the wet
and dry sections of the filter, all at once. There is no disadvantage
in removing the filter media a little at a time but experience has
shown that it is unnecessary to do so. The skimmer is, of course, left
connected to the system and you could add a second skimmer if you feel
so inclined.