This article first appeared in the February 1989 issue of Aquarium Fish Magazine
Glitter Lines: A Series on Reef Aquariums
by J. Charles Delbeek M.Sc.

Part 1: Reef Aquariums: An Introduction

One of the most recent crazes that has occurred in the North American
aquarium hobby in the last 3 years has been the phenomenon of the
miniature reef aquarium. Photos of fantastically beautiful marine
aquariums, filled with lush growths of algae and invertebrates, have
become commonplace in aquarium magazines. Yet these systems continue
to be a source of much confusion, ongoing debate and extreme frustration.
Confusion as to what exactly a miniature reef is; confusion caused by
the bewildering array of filters, lights, and technical gadgets
available; debate as to which filter, if any, is best; debate as to
the type of lighting to use; debate as to the feeding of the
inhabitants and yes; frustration because there seem to be so few
people who can speak knowledgeably about these systems (not to say
there aren't any, just that they are hard to find); frustration
because no matter how hard you try, your tank never looks as good as
the ones in the magazines or the one in Lucky Joe's pet shop down the
street and finally; perhaps frustration because Lucky Joe may not have
a clue why his tank looks good either!

Over the course of the next few months I will be covering a variety of
topics concerning reef system aquariums in such a way as to be of the
most benefit to someone who is approaching the subject for the first
time. That is not to say that intermediate or advanced hobbyists will
not find anything of interest in these articles, I hope to be able to
provide them with some useful and, certain to be, controversial
information too!

This series of articles will cover the basics of filtration, lighting,
nutrition, water chemistry and ecology, necessary to begin to
understand these systems. I say "begin to understand" because no one
really knows "all about" reef aquariums but perhaps together we can
raise some interesting questions and come to some useful conclusions.
Furthermore, I urge you to seek out as much advice as you can from
retailers, other hobbyists, magazines and books. Then go by what you
can see works, not what someone says might work. I will attempt also
to follow each article with a list of references that one can go to
for additional reading. I can not stress enough the importance of
reading. The more informed you become the less likely you are to be
duped by someone less knowledgeable and the more likely you are to
start asking the right questions. The more you learn about the systems
and organisms you plan to keep the greater your chances of success.
Try to also get into the habit of using the scientific names of the
various organisms you are interested in. A Purple Goby can refer to
almost anything, including fish which are not even gobies! When you
use the scientific names everyone will know what you are talking about
and this can save a lot of headaches when discussing animal husbandry
with other hobbyists or ordering livestock. Finally, I strongly urge
you to join a marine aquarium society. It is through such a society
that you can meet other, more experienced marine hobbyists who can act
as a source of practical knowledge and experience.

What is a Miniature Reef?

Gee that sounds like a simple question. Yet, I bet you could ask that
question of 10 different hobbyists and get 10 different answers! The
problem is that everyone has their own image of what a natural reef
looks like. The snag is, not many of us have actually seen a living,
thriving reef! Various authors (e.g. Emmens, 1986) have criticized the
Dutch version of the miniature reef, filled with lush growths of green
macroalgae of the genus Caulerpa, for not being an accurate
representation of the coral reef environment. Natural coral reefs are
not covered with such luscious growths of algae for the simple reason
that there are far too many herbivores present for them to grow to
such proportions. Yet, if the tank works well then why worry? It all
comes down to what type of marine environment you want to recreate and
your vision of that environment. My idea of a miniature reef may not
agree with yours or visa versa but I believe that the following
definition can be applied to all forms:

     A miniature reef aquarium represents the exact flora and
     fauna that one would expect to find under natural
     conditions, maintained in a closed system. It is, in all
     respects, as if a living piece of the environment had been
     transported directly into an aquarium complete with all the
     accompanying substrate, algae, bacteria, invertebrates and
     fish.

The difficulty comes in maintaining this environment in its initial
form. The marine environment is so complex, the interactions between
both the biotic (living) and abiotic (non-living) factors so
intricate, that if only one factor is missing, the whole system will
become drastically different. The Dutch philosophy seems to be to
allow the system to reach and maintain an equilibrium on its own with
the minimum of technology. In contrast, the German philosophy appears
to be to achieve this balance through the use of technological
wizardry. Both have their strengths and weaknesses. In North America,
where this branch of the hobby is in its infancy compared to Europe,
the two philosophies appear to be hybridizing. There are a number of
features that are indicative of reef aquariums. Among these are the
type and amount of light used, the kind of substrate employed, algal
growth and water movement. Filtration is another key element but there
are exceptions, as we shall see later.

Most reef systems are characterized by much higher light intensities
than you are probably used to seeing over an aquarium. Numerous
fluorescent tubes or metal halide light pots are invariably seen over
the majority of reef tanks. I say most reef tanks, since it is
possible to construct low light systems designed to imitate deep water
(>80 ft.) ecosystems dominated by corals that do not contain symbiotic
algae (e.g. some sponges and Dendronepthya spp. soft corals). Except
for the deep ocean vents, light is the basis for any ecosystem and is
therefore essential for reef tanks. The reason for this is that the
algae in the system (both macro and symbiotic), which help to maintain
the environment and provide nutrition for fish and invertebrates,
require adequate light (both intensity and spectrum) to grow properly.

The second major element of any reef system is the use of a certain
type of substrate called "live" rock. The material out of which the
rock is made is not alive but it does contain a multitude of life both
inside and out. Carlson (1987) has proposed the following definition
for live rock:

     A piece of carbonate reef substrate formed by the action of
     living organisms such as corals and coralline algae and
     consolidated as part of the reef framework after the death
     of the original coral/coralline algae and continuing to
     provide shelter and a growing surface for numerous reef
     algae, invertebrates, fishes and subsequent generations of
     corals and coralline algae.

The use of live rock immediately introduces into the aquarium numerous
algae, bacteria and small invertebrates all of which contribute to the
overall quality of the aquarium water. The general recommendation of 2
lbs. of live rock per gallon of water usually quoted is not adequate
in my opinion. The reason for this is that the type of live rock
available varies greatly in density depending on where it was
collected. If you used very dense coral rock, 2 lbs./gal may only give
you five rocks in a 50 gal tank, whereas if you used very porous coral
rock the same 2 lb./gal figure might give 20 pieces of rock, enough to
fill the tank. Julian Sprung (personal communication) makes the more
realistic recommendation of putting in enough rock to reach to 3/4 the
height of the tank with a gentle slope to the front of the aquarium.
Some have questioned the ethical use of live rock and advocate only
using very small amounts over a base of dead rock. The belief is that
the organisms will eventually colonize the dead rock. While this may
happen to a certain degree, in a small closed system the dead rock may
never come close to the original rock in diversity and the initial
rock will probably suffer a decrease in diversity. The exclusive use
of live rock results in a more diverse and, perhaps, stable system.
The majority of live rock collected is composed of old, broken off
pieces of reef rock. The practice of breaking off pieces of living
reef is, of course, reprehensible behaviour and should be condemned.
Live rock "farms" make more sense and should they prove to be both
financially and ecologically sound, will likely become the source of
the future. Controlled collection may also prove to be viable but much
study needs to be done on the exact level of sustainable yield that
can be employed.

The use of algae in marine aquariums to help filter the water is not a
new idea. So called "algae" filters have been used for years in
aquaculture and by hobbyists in Europe (deGraaf, 1981). For many years
hobbyists thought that if they could get a good growth of hair algae
or green slimy algae, they were doing pretty well. Ironic how today
such growths are considered highly undesirable! The use of macroalgae
such as Caulerpa, Halimeda and Udotea was considered to be much too
difficult and best left to the "experts". However, the use of
macroalgae in Europe has been going on for over 20 years and it
remains a mystery to me why it never caught on in North America sooner
then it did! Today we have learned a thing or two from our European
cousins and macroalgae have become major components of most aquariums.
[1996: The use of Caulerpa has grown out of favour due to the detrimental
effects of uncontrolled growth if the macroalage]
Algae perform numerous important functions in marine aquariums. They
help improve water quality by absorbing heavy metals, phosphates and
nitrogenous wastes such as ammonia and nitrate, such that regular
harvesting of algae can act as a method of filtration. In fact,
macroalgae remove mostly ammonia and therefore, indirectly contribute
to lower nitrate levels. The "microcosm" system developed at the
Smithsonian Institution relies exclusively on algal filters, in the
form of algal "turf scrubbers", as its sole means of filtration.
Furthermore, macroalgae produce numerous substances which are released
into the water, most of which tend to improve the "liveability" of the
water for other organisms. When George Smit (1986) first mentioned the
positive effects of "antibiotic" substances released by algae, on the
fish in a reef tank, people generally scoffed and many so called
aquarium "experts" labeled the idea as ridiculous. However, if any of
these "experts" had bothered to read a basic undergraduate textbook on
algal biology they would have discovered that marine algae do release
numerous antibiotic substances as well as carbohydrates, amino acids,
proteins and many other substances (Round, 1981). Algal growths also
add dissolved oxygen to the water, through the process of
photosynthesis, during the daylight hours.

Water movement is something that most people are familiar with,
however, you may not be aware of the different types or their
importance to algae and animals. Since many of the invertebrates and
algae we keep in reef aquariums are sessile (can't change their
location) they develop such that they are adapted to the environmental
conditions in which they grow. Therefore both their shape and
orientation is often controlled by the amount of light available and
the type of water movement they encounter. In addition, these
organisms depend on water movement to bring them food, to carry away
their wastes and to rid themselves of fouling organisms (Sprung,
1988). The three main types of water movement are surge, turbulence
and laminar flow. Surge is the back and forth movement one often
imagines when one thinks of a reef. Surge is caused by ocean swells
and wind-driven waves (Sprung, 1988). As the waves move into shallow
water the circular motion of the water becomes compressed and
flattened, causing the water to move back and forth. This is best
demonstrated by the to and fro motion of large sea fans in shallow
reef areas. Surge is an important factor in the ecology of many reef
organisms, especially flexible ones. The back and forth movement
exposes more of the surface area to light, increases the feeding
efficiency of polyps and greatly helps in the exchange of metabolites
and gases with the water. Turbulence is a random swirling of water in
all directions. This is often caused by opposite currents clashing or
water swirling around objects. Laminar flow is water movement in one
direction and is the type of flow commonly generated by aquarium pumps
and encountered on deeper portions of the reef. Although small scale
turbulence can be generated in aquariums by laminar flow, the effect
is usually isolated and not tank wide (Sprung, 1988). When it comes to
keeping reef organisms we must take into account the area from which
they were collected, since this will determine which forms of water
movement they are adapted to. If you know what to look for, the shape
of the organism is often a clue; books, magazines, photos and
scientific periodicals are possible sources of information. I cannot
stress enough the importance of proper water flow in any marine
aquarium. I remember when I was a teenager, there was a store I used
to frequent that specialized in marines. Their tanks were always full
of swirling masses of tiny air bubbles generated by large water pumps.
The water was always frothing away in those tanks! These were fish
only tanks but the fish always looked very healthy and active. Strong
water movement stimulates fish too, and they certainly seem to
appreciate it! I recently saw a program on the Philippine reefs and
there was a scene in a shallow surge area showing a large anemone
being battered to and fro by the surge. In the anemone were two
clownfish who were frantically swimming back and forth trying to
maintain their position in the anemone, what a sight! Contrast that to
a passive aquarium environment and perhaps you can see what needs to
be improved upon. Recently, there have been a few products introduced
into the market that claim to be "wave generators". They may work to a
limited degree but I believe that there is a great deal of room for
improvement and improvisation.

In the next article we will take a look at filtration in reef
aquariums: the different types and their perceived roles, and trickle
filters and what to look for when buying one.

References

Carlson, B.A. 1987. Aquarium systems for living corals. Int. Zoo Yb.
             26:1-9.

deGraaf, F. 1981.Handboek Voor Het Tropisch Zeewateraquarium. A.J.G.
               Strengholt.

Emmens, 1986. The natural system and the minireef. FAMA 9(9):71

Round, F.E. 1981. The Biology of Algae. Cambridge Univ. Press.

Smit, G. 1986. Marine aquariums. Part One: Is it time for a change?
               FAMA 9(1):35

Sprung, J. 1988. Captive reefs. TFH, October 1988:72-84.


Suggested Readings

Moe, M.A. Jr. 1989. The Marine Aquarium Reference: Systems and
                 Invertebrates. Green Turtle Publ., Plantation, FL.

Spotte, S. 1979. Seawater Aquariums: The Captive Environment. Wiley-
                 Interscience.

Sprung, J. 1988+. Reef Notes. (monthly column published in Freshwater
                 and Marine Aquarium magazine).

Wilkens, P. 1973. The Saltwater Aquarium for Tropical Marine
                  Invertebrates. Uppertal Elberfeld.

I would recommend that you get Moe's book first. It is clearly written
and easy to understand. The other books mentioned tend to be more
technical in nature or require a healthy dose of salt, but all will
give you more than enough information on reef systems.