In the last article, I began a somewhat
in-depth explanation of some of the pervasive myths and misunderstandings
in the reef aquarium hobby. That article, and the current
one, expands upon a presentation I gave at the 2003 International
Marine Aquarium Conference in Chicago. In this part, I will
look at other topics that are still in widespread belief despite
lacking basis, or with evidence to the contrary. It is by
no means an exhaustive treatment, and without question there
are many other myths that need (and will need) to be dispelled
from this hobby, and industry, for future progress in the
field to occur.
Myth 7: Hairy crabs are bad (can eat
corals, etc.) and should be removed.
The hairs or bristles on crabs are extensions
of various appendages and are tactile and/or chemosensory
receptors involved in all manner of behaviors, from feeding
to defense to locomotion. Crabs with the stiff bristles called
setae on their feeding appendages often use them as filters
or combs, and this is equally true of many of the symbiotic
crabs associated with corals. Some coral-associated crabs
are hairy, and some are not. Similarly, some "non-hairy"
and mostly herbivorous crabs, like Mithrax, can and
do eat corals (many others, such as the portunids,
eat fish). Other extremely hairy crabs may not interact with
corals at all, but may be scavengers. It's my experience that
most crabs should be watched closely in aquaria as they tend
to be somewhat nonselective in their feeding choices, but
it is also my experience that crabs found and remaining within
the branches of coral colonies are almost invariably symbionts
and not predators (though the latter do exist), irrespective
of the number of bristles on their appendages.
Potential: relatively harmless,
except, of course, to any crab that becomes the victim of
a wrongful designation. There is some evidence to suggest
that the presence of symbiotic crabs is beneficial to corals,
although the relative benefits to corals in aquaria is more
questionable. In any event, they are not harmful and are certainly
interesting and attractive.
I have heard this repeated since I began keeping aquariums.
Figure 1 & 2. Two hairy crabs from the family Pilumnidae
that are commensal with Pocillopora corals.
Click picture for larger image.
Myth 8: The statement, "but
my water quality checks out fine."
In his articles here (and elsewhere), as
well as in his forum on Reef Central called The
Reef Chemistry Forum, Randy Holmes-Farley provides extensive
information on the nature of common (and sometimes uncommon)
chemicals in reef aquaria. Ron Shimek, and others, have also
covered various topics in chemistry and biochemistry over
time frames spanning ten years and more. Until relatively
recently, only a few chemicals were generally considered in
reef aquaria, and the ability to accurately measure those
parameters has frequently been called into question.
My point above is that aquarists routinely
check a variably complete set of a handful of chemical parameters
in variably accurate ways to make the oft-repeated statement,
"my water quality checks out fine." As has been
discussed elsewhere, there are many difficulties of being
assured that such statements are true, and the more recent
information concerning more exotic and toxic chemical species
including various metals and organometallics virtually ensure
that there might be many reasons to suspect that one's water
quality might not be "fine," despite routine testing
for common parameters.
To take this issue a step further, one
must necessarily include the bounty of organic chemicals produced
by organisms in aquariums called secondary metabolites. I
am both pleased and troubled that the word "allelopathy"
has become a regular word in many aquarists' vocabulary. It
is almost impossible to describe how varied the products of
metabolism can be in the marine environment. In short, virtually
every organism in the tank has them, produces them, and releases
them. The effects of secondary metabolite chemistry are significant
enough to cause real and sometimes dramatic effects in the
wild where dilution effects are vast. So common and numerous
are these compounds that conferences, books, and journals
are devoted entirely to the subject. I would urge readers
to look through a copy of the Journal of Natural Products
to see the scope of this topic (it is only one of many sources
of such information). Each issue consists of several hundred
pages (often filled with 1-2 paragraph descriptions) of metabolites
derived and isolated from natural sources (organisms) and,
sometimes, a brief description of potential effects (usually
based on chemical structures similar to those of known function).
In any given issue, about 20-50 percent of the chemicals are
from marine organisms, and many are from tropical marine organisms.
For example, here are the relative feature articles from the
past two issues alone:
Novel Oxylipin Metabolites from the
Brown Alga Eisenia bicyclis
Isolation and Structure Determination
of Lyngbyastatin 3, a Lyngbyastatin 1 Homologue from the Marine
Cyanobacterium Lyngbya majuscula. Determination of
the Configuration of the 4-Amino-2,2-dimethyl-3-oxopentanoic
Acid Unit in Majusculamide C, Dolastatin 12, Lyngbyastatin
1, and Lyngbyastatin 3 from Cyanobacteria
Semiplenamides A-G, Fatty Acid Amides
from a Papua New Guinea Collection of the Marine Cyanobacterium
Komodoquinone A, a Novel Neuritogenic
Anthracycline, from Marine Streptomyces sp. KS3
Placidenes C-F, Novel -Pyrone Propionates
from the Mediterranean Sacoglossan Placida dendritica
Plakortides M and N, Bioactive Polyketide
Endoperoxides from the Caribbean Marine Sponge Plakortis
New Polyhydroxy Sterols: Proteasome
Inhibitors from a Marine Sponge Acanthodendrilla sp.
New Brominated Labdane Diterpenes from
the Red Alga Laurencia obtusa
Briaexcavatolides S-V, Four New Briaranes
from a Formosan Gorgonian Briareum excavatum
The Synthesis of SO-3, a Conopeptide
with High Analgesic Activity Derived from Conus striatus
New Cembrane Diterpenes of the Marine
Octocoral Eunicea tourniforti from the Eastern Caribbean
Isolation and Structure Determination
of an Antimicrobial Ester from a Marine Sediment-Derived Bacterium
Identification of New Okadaic Acid Derivatives
from Laboratory Cultures of Prorocentrum lima
One can imagine what twenty years worth
of this type of research has produced. In the feature articles
of the past two issues of a single journal, we see novel chemicals
derived from sponges, soft corals, dinoflagellates, bacteria,
algae, cyanobacteria and mollusks. These are, of course, in
addition to those already known from these organisms. Some
sponges, algae, and soft corals have been identified that
produce in excess of 40 separate chemical compounds.
They are termed "secondary metabolites"
because in many cases these compounds do not seem to have
a function in basic metabolism. However, many are extremely
bioactive, and have diverse effects on other organisms, including
being lethal. Of course, the effects are largely unknown and
many of these chemicals are not produced to have an effect
on organisms that would not ordinarily be encountered by the
producer of the compound. Other compounds may have an unintentional
effect. Furthermore, various compounds may be very specific
in the species they affect, and in how they affect those species.
In almost all cases, pairwise tests of one species on another
have not been done for any effects. There is little to no
information as to what the ultimate fate or reactivity of
these organics products might be in any environment, much
less in aquaria. Finally, these bioactive compounds are highly
concentrated in the closed small water volumes of our aquaria.
For some examples of the scope of secondary metabolite chemistry
from coral reef organisms, see the boxes below
which I have derived from various primary and secondary literature
over the years. The listings in the boxes are by no means
I hesitate to make such seemingly alarming
statements, for I am concerned that such "unknowns"
may become the fuel for more myths. It would be comparatively
easy for such information to be used as an excuse on which
to blame the death or failure to thrive of various tank inhabitants.
However, the fact that virtually every inhabitant in our aquaria
is producing variable amounts of novel, uncharacterized, and
well-known bioactive secondary metabolites of mostly unknown
effects, and may be reactive with a host of other largely
unknown organic and inorganic compounds present in our tanks,
makes our water a complex soup with no two tanks being alike
- or predictable.
The take-home message of this myth is that
it is practically not possible to say "my water tests
fine." All we can do is recognize certain facts, and
act accordingly. In my opinion and experience, the most pragmatic
solution is dilution and absorption by the use of water changes,
protein skimming, and activated carbon. I fully realize the
many issues that might stem from this simple advice, especially
in light of the materials provided by authors as mentioned
above. However, if nothing else, it seems to potentially simplify
the many potential chemical interactions that might be occurring.
Potential: Innocuous to lethal.
I believe many inexplicable problems in the survival of aquarium
species may be due to secondary metabolites. Some are well
known to occur, others are purely speculative. However, there
remains the incontrovertible fact that there are effects,
and that every reef aquarium has organisms producing a pharmacopoeia
of bioactive compounds.
Every day, aquarists around the world use hobby test kits
to measure the levels of perhaps 1-6 variables for which tests
are available. There are no tests available for the 4-Amino-2,2-dimethyl-3-oxopentanoic
acid unit in Majusculamide C, Dolastatin 12, Lyngbyastatin
1, and Lyngbyastatin 3 from Cyanobacteria that were discovered
last month. For all we know, this unit causes 100% mortality
in Trachyphyllia geoffroyi. Then again, it might not.
Some Typical Reactions Of Marine Invertebrates To Bioactive
(Compiled from various sources)
- Tissue hypertrophy
- Increased secretion
- Change in mucosal composition
- Change in mucus secreting cells
- Feeding response initiated
- Polyp withdrawal
- Formation of sweeper tentacles (stony/soft corals,
- Formation of acrospheres
- Change in growth pattern
- Change in growth form/direction + or -
- Change in nematocyst composition
- Tissue necrosis - local or general
- Initiation of spawning
- Cessation of gonad development
- Change in metabolism
- Change in behavior (non-sessile invertebrates)
- Increased or decreased susceptibility to disease
- Increased or decreased growth rate and survivability
- Increased or decreased settlement of larvae
- Iincreased or decreased fecundity
Potential Roles of Marine Bioactive Compounds for the
(Compiled from various sources)
Defense against predation
- Other anti-predation (mollusks, echinoderms, etc.)
- Foul odor
- Bad taste
- Antisettlement (larvae, competitors, etc.)
- Mediator of growth form, growth hormones
- Phototaxis, geotaxis?
- Discharge of nematocysts
- Inter- and Intra-specific communication, chemotaxis
- Admittance, specificity and non-digestion of algal
- Allelopathy against allogeneics and xenogeneics, b/t
and w/in taxa
- Stunting, necrosis, avoidance, mortality
- Immunological responses
- Mass spawning, spawning release factor?
- Polyp contraction/egg release
- Surface brooding/mucus sheet formation
- Nocturnal spawning
- Egg buoyancy
- Sperm attractants
- Egg and planulae anti-predation
- Species recognition molecules
Myth 9: Lugol's dips or other commercial
dips are useful or prophylactic for treating coral ailments.
Myth 10: Bacterial infections are common in aquarium corals.
I have discussed this extensively in other
columns, and so I will be very brief here. To date, there
is no disease of aquarium corals that has been
shown to have a bacterial cause. There are unquestionably
bacteria that can cause disease in aquarium corals, and bacterial
infections of aquarium corals may be relatively common. However,
I doubt it. There is at least one genus of ubiquitous bacteria
that has been isolated from corals (Euphyllia species,
Catalaphyllia jardinei, and zoanthids) that also causes,
or is part of the consortium that causes diseases in wild
corals. It is a species of Beggiatoa, and it is often
visible as white filaments or webs, occasionally becoming
like mats or paste as the colony increases in density. Beggiatoa
are gliding filamentous bacteria that tend to form cottony
colonies or mats at interfaces between aerobic and anaerobic
zones in terrestrial, freshwater, and marine environments.
They oxidize hydrogen sulfide produced in the anoxic zones,
but can also grow heterotrophically using acetate as a carbon
source and some can autotrophically use carbon dioxide. These
microbes are found on sediment and substrate surfaces, including
corals. They provide a valuable function in nutrient processing,
and cannot be "eliminated." Being opportunistic
coral pathogens to some species is unfortunate, but I am afraid
it must be viewed in terms of the root factors that may have
been involved in a coral becoming colonized and infected by
Beggiatoa in the first place.
Other bacteria commonly thought to cause
disease in aquarium corals are the numerous, and often yet
to be described, Vibrio species. Vibrios are
common on coral surfaces, and some, but not all, are known
to be potentially pathogenic. However, the conditions under
which they become pathogenic are largely unknown, and whether
or not they are opportunists is similarly unknown. Furthermore,
in no case have they been found as a disease-causing agent
in aquarium corals.
Even if bacteria were someday found to
be a problem for aquarium corals, recognizing the signs that
would unambiguously indicate a bacterial infection would be
extremely difficult or impossible. Thus, treatment options
will be very difficult. After all, if you simply see recession
on a coral how is it known if it is due to shading, poor water
flow, allelopathy, or bacteria? The answer is that you probably
If this is the case, why not just use antibiotics
or antiseptic dips prophylactically? The answer to this question
is that both the coral and the normal bacterial flora (some
may be symbiotic) growing on the coral surface produce natural
antibiotics, mainly to non-native strains. Therefore, anything
that kills potentially bad bacteria will certainly also be
killing good bacteria. This, in itself, compromises the aggregate
of coral and bacterial defenses to colonization by new strains
and reduces natural immunity. Additionally, there is little
or no information on the effect of various substances and
drugs used as antibiotics on the coral itself, and at least
some of these products are moderately toxic to corals (see
In cancer chemotherapy, the theory behind
treatment is that you hope to preferentially kill more cancer
cells than healthy cells. In the process, the patient takes
a beating. Sometimes it works, sometimes cancer continues,
and sometimes the patient dies from the treatment. Based on
my own experience, I can say that treating corals with unknown
agents results in the same three possibilities. If a coral
is recently purchased, it is already likely to be stressed,
and further stress of "prophylactic" treatments
may result in the mortality of a specimen. Of course, this
"theoretical" discussion all operates under the
assumption that 1) the substance is actually effective against
whatever is being treated and 2) that there is some knowledge
of the cause of the disease at all.
In my experience, Lugol's iodine solution
is moderately effective at treating corals with brown jelly
infections and seems reasonably well tolerated by most (but
not all corals). Otherwise, I have not noticed Lugol's solution
to be a particularly useful treatment for other problems in
aquarium corals. Speaking of brown jelly infections
Myth 11: Brown jelly is caused by
the protozoan, Helicostoma nonatum.
I have found occasional references to the
Family Philasteridae of the Ciliophora containing a species
named Helicostoma notata. I have browsed books on ciliates,
and found no reference to any affiliation between the genus
Helicostoma and corals. I have found no reference to
support that brown jelly infections are caused by protozoans
or ciliates, except those based on a German book on reefkeeping
and an article in a German aquarium magazine from the mid
1980's. Since then, this designation has been promulgated
throughout the world to the point where an internet search
yields only two non-aquarium based references to the genus
Helicostoma in total. I can find no valid reference
to H. notata or H. nonatum, and one reference
to an H. brudderbuckii. In fact, the few volumes I
can find that mention Helicostoma consider it to be
monotypic, consisting of the species H. oblongum. The
characters of H. oblangum do not fit the characters
of the ciliates I have found in brown jelly, either, as might
be expected since this ciliate is mentioned being found in
brackish or salty water of the New York bight. A search of
database confirms that this is the only valid species.
In fact, even an Australian science publication has erroneously
called brown band disease as attributed to this ciliate (again,
without any reference at all). The point here is that while
ciliates are present in the brown jelly material, it is not
clear at all what role, if any, they play in brown infections.
They might easily be present simply because of the dead tissue.
However, the ciliates are mostly of one kind, and there are
ciliates present in all samples. What ciliate is anyone's
guess at this point, and there may be many. I suppose it might
even be Helicostoma nonatum, but I do not believe this
ciliate has been accurately identified in corals with brown
Figure 3. In this photo, a brown jelly infection has
begun on a Pocillopora damicornis colony.
Figure 4. A few hours later, the jelly like material
has consumed the branch tips
still visible above. The outlines of the branches are still
visible in this
amorphous mass of digested tissue and zooxanthellae.
What I have done is examine brown jelly
from three affected corals: a Euphyllia ancora, a Pocillopora
damicornis, and a Plerogyra sinuosa. The samples
were all from different tanks, and collected many years apart.
I have also sampled a brown jelly-like material from a reef
coral in the Caribbean, and a sample of a brown slimy flocculent
material that is relatively common on substrates in the Caribbean,
usually from reefs that are not doing very well. I have not
yet had a chance to examine the wild material. However, one
sample of brown jelly now resides with the Registry of Coral
Pathology, and the description by coral pathologist Esther
Peters, confirms that there is coral tissue material, both
algae and animal, within vacuoles of the protists. The necrotic
condition of the coral tissue, and the fact that ciliates
are not found digesting nearby corals or even healthy tissue
of the affected specimen suggests they may just be opportunists
of necrotic tissue rather than causative, or that they are
part of an as yet unidentified consortium. I am slowly getting
to these other samples, and hope to have more information
Potential: innocuous to very
harmful. The use of experimental treatments may have no effect
at all, or it may result in mortality of the treated coral.
I have watched the polyps of Pocilloporids bail out of their
skeleton within an hour of being exposed to experimental treatments,
including Lugol's solution. The use of antibiotics may also
be harmful, in general, when applied without diligence in
the creation of AB-resistant strains. Playing "doctor"
with corals may seem compassionate and impressive, but mostly
its just irresponsible guesswork, often with the hopes that
some miraculous "cure" might result to save corals
from unseen and unknown pathogens.
Distribution: extremely widespread,
and has been occurring over long periods of time.
Myth 12: Aquariums need supplements
from the fish store.
Again, I refer readers to the many articles
published by Holmes-Farley and Shimek. It has become obvious
we know little about the chemistry of aquaria, and it has
long been known we know very little about specific requirements
of corals and other reef aquarium inhabitants to exotic elements.
It is equally apparent that the use of various foods and salts
result in all manner of elevations in water chemistry that
There are a relatively few things that
are quickly depleted in aquaria, or that are generally absent,
that have numerous and documented functions in many organisms.
As far as I am aware, these things consist principally of
calcium, carbonate, iron, iodine, oxygen, and plankton. Of
these, iodine is of questionable utility as an element in
solution to most species of interest to aquarists, although
the use of algae in refugia is a perhaps more recent interest
and one that may, according the species grown, be of concern.
I will not pretend to guess at the myriad
potential requirements of every organism nor the presence
or absence of every potential element in a tank. What I can
say is that I have not personally added any supplement from
a fish store to my tank in six years, and I have not regularly
dosed any supplement for eight years, with the exception of
calcium, carbonate, and foods. In that time, I have not seen
any specimen or population decrease, fail to thrive, or vanish
as a result. Admittedly, I have not done any study to confirm
my observations, nor am I sure that some ignored or unseen
population has not been lost as a result of my omissions.
However, I would also say that no evidence exists to show
that any aquarium supplement other than those mentioned above
has resulted in any specimen or population increase in growth,
health or survival.
The aquarium trade is astonishingly fast
to react to trends in the market, and to capitalize on the
passion and excitement of aquarists' desire for magic bullets.
The labeling and claims of virtually all such manufacturer's
read like the sound of a broken record, all claiming to produce
dramatic results and seeming to require their purchase. The
recognition of elevated metals in aquaria, discovered within
the past four years and only becoming a major topic of interest
within the past two years, has already resulted in manufacturers
producing products claiming to address these problems and
be equally as miraculous and required as their previously
or concurrently produced "high metal" predecessors.
I find it funny to imagine how the "research and development"
teams that must certainly be sitting behind lab benches in
white jackets with corals in research systems never picked
up this problem - until now, of course, after the real researchers
in the hobby have made the real discoveries (with no credit
by the companies of course, but sometimes with criticism in
advertisements, I might add) and have adjusted to market demand
with the appearance of the "new and improved" products.
Potential: harmless to lethal.
Since many supplements are mostly water, the primary harm
is to the wallet of the aquarist.
In other cases, aquariums may be compromised by the appearance
of nuisance species that take advantage of normally limiting
nutrient sources. In the worst case, the supplements are toxic
Distribution: global. The
purchase of unnecessary supplements may be as much testimony
to the effectiveness of advertisement and the international
distribution of such products as to the intrinsic nature of
humans to desire such things.
Myth 13: The refugium concept.
The now-common practice of maintaining
"refugia" is a welcome advance to the reef aquarium
hobby. The concept, as far as I can recall, originated with
the design of the Smithsonian Caribbean mesocosm in the 1980's.
As an offshoot of the technology that was used in that display,
algal turf scrubbers were licensed to Inland Aquatics, who
soon offered drop-in refugia to retrofit existing tanks not
utilizing turf scrubbers. In the 1986 book, Dynamic Aquaria,
Adey and Loveland write, "Most of our refugia have been
directed towards freeing attached fleshy algae, soft-bottom
invertebrate populations, and plankton from severe predation
by fish and larger invertebrates (particularly crabs and lobsters)
general, the semi-stability that is achieved in community
and population structure in the wild over large areas, and
at time scales of centuries and millennia, is achieved in
microcosms, mesocosms, and aquaria by the manipulation of
space (refugia) and, when necessary, the populations themselves."
In any case, the rest is proverbial history.
Now, do-it-yourself refugia and commercially available refugia
exist at every turn and are very common in today's reef aquaria.
As mentioned, the idea behind refugia
was to provide an area safe from constant predation for the
many small organisms that were quickly eaten in displays housing
large populations of fish and predatory invertebrates. Macroalgae
were often incorporated into refugia as both food sources
and habitat. Soon, the rich flora and fauna that tended to
grow in refugia was exploited as a recovery area for sick
fish, and could act as a nursery for breeding species in some
cases. Of course, the size of the refugium might limit how
many predators (as adults or juveniles) might be able to temporarily
As more aquarists began to utilize these
small, attached tanks, the ideas behind them were both improved
upon and also bastardized. Soon, mud- and Caulerpa-filled
sumps became commercially developed as a natural filtration
method. Aquarists using these systems noted the luxuriant
growth of the same populations mentioned above, and likely
also noticed how they rather resembled things called refugia.
Other aquarists took advantage of a new tank in the system
utilizing the same water in which many of their corals were
thriving, and the refugia began doubling as coral propagation
tanks. Of course, the corals appreciated the extra available
food, too. All too soon, photographs of refugia with one or
two fish, or some shrimp, began appearing on websites. The
refugium had become a low flow, specialized habitat reef tank
with predators whose primary purpose was really denitrification
through the use of sand beds and large quantities of the toxic
algae, Caulerpa species.
The concept that macroalgae and sand beds
could be used in refugia as nutrient uptake began in the 1980's.
The widespread use of them as such seemed to be a novel concept
to many, though it wasn't. However, it was a welcome use and
a wise idea to incorporate them to many systems. Yet, refugia
by themselves are generally quite small, and the largest fraction
of nutrient processing of a tank is probably happening in
the larger fraction of the system. In other words, small refugia
with sand and macroalgae are supplemental to the processes
and uptake happening in the bulk of the tank. Most aquarists
keep one to many herbivorous fishes in their tanks, in addition
to the many herbivorous invertebrates that are major grazers
of algal biomass. Just as in the wild, with low nutrient levels
in the tank, algal control is a top-down process where grazing
limits algae within the main reef system. If anyone doubts
this to be the case, remove all the herbivores from a well-lit
reef aquarium and watch what happens. Turf algae will begin
growing rapidly. It is not the magical properties of Caulerpa
in action, it is just ecology.
I am not in any way condemning the use
of macroalgae in refugia. I am very fond of many of them,
although many have quite numerous and toxic secondary metabolites,
like soft corals and sponges. In particular, I am very unfond
of Caulerpa (Figure 5). It is invasive and very difficult
to eradicate. It is toxic to fish and has many metabolites
- and releases them when the organism degenerates during spawning.
Acidic rhizomes etch carbonate (Figure 6) and these algae
can kill other more desirable species by overgrowth. I have
had it grow right through the stalks of soft corals. Many
aquarists say that it has not been a problem for them. My
response? Just wait. It will. I guess my big question regarding
Caulerpa is why use it at all when so many more desirable
species of macroalgae exist, like Chaetomorpha species,
or others (Figures 7 & 8).
Figure 5. One of many species of Caulerpa, this
is C. racemosa var. peltata.
Figure 6. Caulerpa uses its rhizomes to attach
tenaciously to substrates - a factor
that makes it difficult to remove.
Figure 7. Dragon's tongue algae, Halymenia sp.
Figure 8. A hardy version of the red algae, Gracilaria
To restate yet again, a refugium is
a place provided to allow certain organisms to grow while
freed of predation or herbivory. If one incorporates predators
such as shrimp, fish, and corals into a refugium, the very
reason for its existence is lost. Given the small size of
most refugia, a handful of zoanthids and a couple shrimp will
likely decimate any populations of small organisms that were
originally supposed to breed and feed the main display tank.
If one desires to keep an area for breeding or propagating
organisms, it might be a tank that replicates a habitat and
that may look like a refugium - but it is not a refugium.
If one desires to have a display tank filtered by natural
processes, it should be ideally (significantly) larger in
scale than the display to be effective. Otherwise, any natural
filtration is probably largely supplemental to what is already
occurring in average reef aquaria, although I imagine with
careful consideration it might become quite significant. The
natural filtration of the display was already initially addressed
with live rock and sand beds (Berlin, ATS, and Jaubert methods).
Protein skimmers provide more than enough additional filtration
in most other systems (Berlin method). A refugium design should
incorporate food sources and habitats that are conducive to
the growth and reproduction of organisms that would otherwise
become food for the mouths present in a reef aquarium display.
In all likelihood, these same elements will also provide additional
benefits such as nutrient uptake and regeneration.
As a final point, many aquarists comment
on the amount of small crustacean life in refugia - and there
often is. However, many of these same crustaceans are benthic
or demersal zooplankton, and are often associated with reef
structure and cavities. Providing a fair amount of rubble
in refugia is a good idea. In fact, I would suggest (and know
personally for a fact) that most people would see far more
crustaceans in a refugium filled with live rock rubble that
is allowed to have turf algae grow on it than in the macroalgae
and sand dominated refugia that are common today. The difficulty
will be keeping enough turf algae growing as fast as the amphipods
Potential: slight to moderate.
In most cases, a refugium of any sort provides some benefit,
although it may be largely functionless for the desired purpose,
depending on the species it contains. The only real risk may
be with the inadvertent mass release and death of some macroalgae
species during spawning events.
Distribution: moderate. The
use of refugia is widespread but may be most common in the
United States. Refugia, while common, are certainly not standard
incorporations into most reef tanks yet.
This concludes the second part of my series
on common myths in reef aquarium keeping. I had hoped to conclude
the series with this installment, but there was a bit too
much information in this installment to make the article length
manageable. As a final offering, I suggest revisiting the
first part of last month's article
on the definitions of anecdote and the benefits of skeptical
thinking. The reef aquarium hobby is filled with amazing insights,
unreported observations, vast stores of knowledge (often unrequited),
a few lies and untruths, and a whole lot of hearsay. It is
everyone's responsibility to think and read and learn before
doing and, worse, repeating things that may not be exactly
as they are said or appear to be. Until next month, please
visit my author's forum for questions or comments about this