Live Rock Algal Succession in a Reef System
by J. Charles Delbeek, M.Sc.

One of the most fascinating aspects of an aquarium filled with live
rock, is the multitude of life forms which these structures contain.
As a reef tank matures the composition of fauna and flora, on and in
the live rock, changes also. Watching and charting these changes can
be as fascinating as watching the invertebrates and fish. One of the
most commonly heard comments about live rock is that it is constantly
changing and new life forms can appear as much as two years later.
Even rock which appears lifeless can, under the proper conditions,
produce new and vigorous growth. However, without a doubt the
greatest changes in the algal composition occur within the first year.

The System
Right from the beginning I would like to say that this was the way I
set up my aquarium. It  does not mean that it is the only way or the
best way, only that this was the I decided to do it. Approximately
eight months ago I set up a custom 30 gallon reef tank after many
months of hesitation and observation of friends' aquariums. Once I
was sure that I could do so with some hope of success, I set about
designing and constructing my own filter. I settled upon a design
utilizing a trickle filter filled with 5 gallons of Dupla BioballsTM
and a wet filter made from a standard 15 gallon aquarium. Water is
first collected by a two stage prefilter. The first stage consists of
a slanted glass plate extending along one side of the tank. Water
flows over this plate, through a hole in the side of the aquarium and
into a 5 gallon aquarium located beside the tank. This holds a small
internal skimmer and a sponge prefilter (this set up has since been
replaced by a larger prefilter tank housing a Tunze 215 power
skimmer). This arrangement allows me easy access to the prefilter for
cleaning and my overflow can act also as an algal filter. The dry
filter uses a drip plate for water dispersion and air is pumped into
both the top and bottom for thorough air saturation. The air entering
the dry filter is first passed through an air filter containing two
chambers. The first contains distilled water to absorb any
water-soluble airborne pollutants, while the second chamber contains
granulated activated carbon (GAC). A short note about your trickle
filter. The growth of bacteria which convert nitrite to nitrate
(Nitrobacter sp.) is inhibited by light. Therefore, you should keep
the dry filter dark to promote effective nitrification (see also Moe,
1989). From the dry filter the water passes into a sediment trapping
section of the wet filter. This consists of a slanted plate which
allows heavier sediments to settle out. The water then flows through
a small chamber which houses about 500 g of GAC, a PolyfilterTM, a
ceramic heater and a temperature controller sensor. Finally, the
water flows into the sump where it is pumped back into the aquarium
via a surface return and another return situated behind the rocks.
The sump contains a float switch to protect the pump from running dry
and a float valve which automatically adds water to make up for
evaporation. An additional powerhead in the tank provides extra
turbulence.

The filter was cycled separately from the main aquarium using the
method outlined by Siddall (1988). While the filter was cycling the
main aquarium was filled with distilled water and power filtered over
GAC and a PolyfilterTM. After one week salt was added and external
filtration continued. Once the filter had cycled, it was emptied and
refilled with freshly prepared saltwater. The purpose of this was to
remove any accumulated nitrates which may have been produced by the
nitrification cycle. The dry/wet filter was then connected to the
main tank and live rock was added.

Lighting consisted of 2-40W Actinic 03 (since upgraded to 60W) and
2-40W Sylvania Daylight fluorescent tubes times on a 12:12
photoperiod. In addition, highly efficient reflectors, kindly
supplied by Web Wheeler of Nautilus Aquatics, were added 4 months ago
and they have effectively increased light output by 80%. I feel that
60W actinics should by the minimum wattage used on aquariums. The 24"
40W models are excellent for small aquariums (e.g., less than 30
gallons) but anything larger should use the 60W. Since switching to
60W bulbs my mushroom anemones have increased 25% in size.
Furthermore, Sprung (1989) recommended the use of 60W in the majority
of lighting configurations he discussed. Incidentally, for those of
you who are concerned about the possibility of UV damage associated
with actinic 03 bulbs I would point out;that Vita-Lites and Daylight
fluorescents produce far more UV than actinic 03's do and, to the
best of my knowledge, I have never heard of any health problems
associated with the use of Daylights and Vita-Lites in everyday
applications (see Moe, 1989, for spectral distribution charts of
these bulbs or contact the manufacturers directly). If any bulb may
have to much UV for your tank it might be the HO or VHO Daylight
bulbs. You may require a UV absorbing shield if your invertebrates
exhibit any adverse reactions (i.e., retraction of polyps on the side
closest to the light source) when using such bulbs.

The live rock was added in two stages, 30 lbs. of seeded rock first,
followed by an additional 50 lbs. The reason for this was simply the
limited availability of the rock. The live rock has been seeded by
the supplier for one month in an unlit aquarium. By the time the rock
was added the main aquarium it lacked any visible non-calcareous
algae but was covered with various species of red and purple
coralline algae. No substrate was used in the system to prevent pH
depression and precipitation of carbonates. The lack of substrate
reduces also the chances of oxygen deprivation due to bacterial
action on accumulated detritus. In addition, the lack of a calcareous
substrate may limit the deposition and subsequent utilization of
dissolved organic phosphate by microalgae and bacteria. It is well
known that many marine algae can liberate bound phosphate, in the
presence of calcium, through the external action of released enzymes
(alkaline phosphatases). When inorganic sources of phosphate become
limited, the synthesis of alkaline phosphatase increases and external
organic phosphate sources, such as glycerophosphate, are then
utilized by the algae (Lobban et al, 1985). It is very important to
keep both inorganic and organic forms of phosphate to extremely low
levels (ppm or lower) in reef tanks which contain calcium carbonate
bearing organisms. Not only do excessive phosphate levels encourage
the growth of undesirable microalgae, but they inhibit also the
deposition of calcium carbonate in both corals (Moe, 1989) and
coralline algae (Brown et al, 1977). In the eight months since
system set up there have been no breakouts of "slime" algae and very
little "hair" algae. I cannot say that I have absolutely no hair
algae, but the amounts are insignificant compared to other tanks I
have seen of comparable age. I attribute this to nutrient suppression
of algal growth through the use of distilled top-off water, limited
nutrient input, frequent removal of accumulated detritus (a source of
organic and inorganic phosphate, see Moe, 1989), and the use of
invertebrate herbivores (8 specimens of the marine snail Astrea
tecta). Since the system has been running, there have been no
measurable levels of ammonia or nitrate. The pH reaches a high of 8.3
during the day and drops to around 8.2 by morning (all measurements
made with Aquarium Systems testing kits). The KH of the water remains
at 13 (Sera KH kit) after having been brought to this level, within
the first few months, through the use of SeaChem's Marine BufferTM.
Water changes are performed at the rate of 5% every two weeks.
However, I found that my distilled water had a rather low pH (5.0) so
I added sodium bicarbonate and sodium carbonate to raise the pH to
8.0 before adding it to the tank. Since doing this neither my pH or
KH have fallen appreciably.

Algal Succession
Succession is an ecological concept which basically describes a
step-by-step change in the fauna and flora of an area over time until
a stable community, the climax community, is reached. There are two
types of succession, primary and secondary. Primary succession occurs
in areas where no living organisms had occurred before while
secondary succession occurs in an area after some disruptive event
eliminates the previous life forms. In the case of live rock, most of
the organisms are usually removed and the denuded rock is used in the
aquarium. I believe that this results in a period of secondary
succession whereby the rock undergoes a series of changes until it
reaches a climax condition. This climax community will reflect what
your rock originally looked like when it was collected. This assumes,
of course, that the same conditions of light and nutrients exist in
the aquarium as at the original collection site. Studies of secondary
succession in coastal marine environments appear to closely resemble
that found in enclosed systems. Murray and Littler (1978) found that
blue-green algae, filamentous algae and encrusting diatoms were the
dominant algae (pioneer species) in the early successional stages of
previously cleared intertidal areas. These were then succeeded by
various macroalgae in a few months. This appears to be similar to
what happens in newly set up reef tanks which utilize large amounts
of live rock. Various undesirable microalgae predominate at first but
gradually disappear to be replaced by macroalgae. If nutrient levels
remain high, however, it may be that these pioneer algae continue to
dominate, resulting in a microalgal mess.

The majority of the algae described in this article were identified
with the aid of Marine Plants of the Caribbean: A Field Guide from
Florida to Brazil by Littler et al (1989). This is an excellent
reference for any marine hobbyist/naturalist who has ever asked the
question "What's that growing there?"; I highly recommend it!

Within five days of adding the first amount of live rock filamentous
algae became noticeable on the glass and some of the rock. This alga
was identified as Bryopsis sp. and reached a peak in growth within
one month; only small amounts now remain. It appears that this is one
of the most commonly encountered algae in newly set up aquariums and
usually disappears within a few weeks (J. Sprung, personal
communication). However, I have noticed that small blooms can reoccur
with changes in temperature and after large water changes, indicating
that it may be an opportunistic species which appears after
disturbances in the environment. This is very similar to what happens
on land where weeds are the first plants to colonize a recently
disturbed area of land. Once the Bryopsis began to disappear,
numerous red and brown algae started to emerge. Among some of the
first arrivals on the rocks were the green algae Anadyomene sp.
(green lacy fans), Cladophoropsis sp. (green thin rods growing in
clumps), Neomeris annulata (short green stalks, partially
calcified), and the green calcareous algae Udotea sp., and
Halimeda sp. Of these forms the Halimeda, N. annulata, Udotea
and Cladophoropsis appeared to carry through. The other species
have been replaced by Ernodesmis sp. (green tubules) and Valonia
sp. (green bubbles). In the overflow, Enteromorpha sp. and
filamentous algae predominate and are harvested regularly. Among the
brown algae Spatoglossum sp. and Padina sp. appeared within the
first three months but have since disappeared. Within 2 months the
tank had become dominated by the brown alga Dictyota sp. As can be
seen from the photos these growths grew quite large and some had an
iridescent blue tinge. Various red algae appeared on the live rock
quite early and most have remained prominent. These algae appear to
grow best in the relatively low light intensity areas of an aquarium
and grow quite well provided they have an adequate nutrient supply.
These included Halymenia sp. (red leafy alga), Kallymenia sp. (a
small red alga which grows in darkened areas), Chondria sp. and
Gracilaria sp. All of these species are still in evidence after 8
months. However, the largest changes appeared around month four. At
this time the Dictyota sp. began to decline and the green alga
Dasycladus vermicularis became dominant. This species has remained
the most dominant species and I believe that this condition
represents the climax condition for this rock. This was further
supported by the supplier who indicated that the rock was originally
covered with D. vermicularis when first collected. Within 5 months
various species of Caulerpa began to appear and at this time
growths of the following species have appeared: Caulerpa
sertulariodes, C. racemosa, C. peltata, C. mexicana and C.
serrulata. One point about Caulerpa that various articles seem to
neglect is that they can be deadly to various corals (soft and hard)
if they are allowed to grow over them. Many species of algae, not
just Caulerpa, are capable of producing various toxins which allow
them to compete for space with other benthic organisms. These toxins
will damage corals and therefore, Caulerpa should not be allowed to
overgrow ANY sessile invertebrate. In fact, I prefer the use of red,
brown and green calcareous algae such as Halimeda and Udotea,
over Caulerpa since they grow more slowly, are readily controlled
and are not as dangerous to the other inhabitants. I have a small
piece of soft coral (Sinularia sp.) that was actually pierced by a
growing runner tip of C. sertularioides. The coral remained
collapsed until I removed "Zorro's blade"!

Animal Population
The animal population has been increased slowly over the last 8
months and consists of small colonies of various soft corals. There
are three specimens of Leather Coral, Sarcophyton glaucum, an
unidentified Sarcophyton, and a specimen of Cauliflower Coral,
Sinularia diversa, all of which have shown marked growth and
development. There are three colonies of mushroom anemones
(Corallimorpharia), blue, green and red. There are also two colonies
of an unidentified Alcyonium soft coral, a small colony of
Sinularia brassica, a specimen of Lobophytumand a colony of
Green Star Polyp (Pachyclavularia viridis). Several colonies of
zooanthids, Palythoa and Parazoanthus (Yellow Colonial Anemones)
grow on some of the rocks as well as various small fan worms,
tunicates, amphipods and isopods. There are two colonies of hard
corals in the tank, a group of Christmas-Tree fan worms embedded in a
colony of Porites and a very small (1/2 inch diameter) Goniopora.
The Porites has since been damaged and is slowly wasting away while
the Goniopora has shrunk in size but no damage or tissue necrosis
is evident.

At one point a colony of the soft coral Xenia was purchased and I
hoped that it would develop into a colony of rhythmically pulsating
polyps. However, it soon became covered with a thin, brown,
sheet-like growth. Subsequent investigation of the coral revealed it
to be dying (i.e., it stunk to high heaven; Xenia normally has an
unpleasant smell but this was worse!). When I examined the mysterious
brown substance under the microscope it turned out to consist of
millions of ciliate protozoans! I believe them to be Heliocostoma
notatum but did not attempt to identify them exactly. Wilkens and
Birkholz (1986) believe that they may only be opportunistic feeders,
that is they only attack previously damaged corals and are always
present in any system. However, J. Sprung (personal communication)
believes that they are more likely parasitic in nature and has had
them appear on, and destroy, previously healthy corals. I tend to
side with the former, since no other corals in the system were
affected.

Many of you who have kept Leather corals are no doubt aware that they
periodically close up, only to reopen in a few days. The generally
accepted explanation for this is that this is a natural anti- fouling
response. When they reopen, a layer of slime is released, much like
shedding skin. This layer carries with it any bacteria and algae
which were attached. However, I have also seen specimens that were
covered with algae which they did not seem to be able to shed. An
hypothesis that I would like to propose is that another function of
this shedding may be as a release of excess carbon! Davies (1984)
postulated that the hard coral, Pocillopora eydouxi, needed to shed
mucus in order to get rid of excess carbon which was produced by the
photosynthetic activities of it's zooxanthellae. Therefore, excessive
mucus production in Leather corals may be an indication of sufficient
or excessive lighting. It is probable that a combination of effects
lie behind this phenomenon.

There were only four fish in the system at the time the photographs
were taken, a 3 cm Redheaded Goby (Gobiosoma puncticulatis), a 2 cm
Cherub Fish (Centropyge argi) and a pair of Green Clown Gobies
(Gobiodon rivulatus), all of whom feed directly from the system and
are only given occasional (once/month) additional feedings. To really
encourage a healthy and diverse growth of algae and other organisms
on your live rock, I would recommend holding off the purchase of fish
until at least 4 months after the tank is set up. Longer is better, a
year is not unusual in Holland. The longer you can resist the
temptation to add fish, the more your rocks will develop and the more
beautiful your tank will become in the long run.

In summary, the tank system that was set up appears to be well on its
way to becoming a stable environment. However, it does not appear
that the original diversity that was originally present has been
maintained. Many of the amphipods and polychaetes seem to have
diminished yet new organisms have appeared that were not originally
present. Whether this is an artifact of a closed system is not clear
but it seems probable that a limited food supply may greatly regulate
the diversity of organisms in a small aquarium. In Holland, hobbyists
spend many evenings closely studying their aquariums and live rocks.
Some go so far as to keep detailed notes and sketches over a period
of many years. If you really want to promote the use of your reef
tank as an educational tool for the whole family I would urge you to
do likewise. Perhaps periodic photos/videos of your aquarium over a
one year period would be easier and open up a whole new world of
enjoyment for yourself and your family. I know, because my father has
constantly been sitting in front of the tank, nose to the glass,
scrutinizing the rocks and their contents, so much so that I can't
even get a look at my own tank anymore!

References
Brown, V., Ducker, S.C. and K.S. Rowan. 1977. The effect of
orthophosphate concentrations on the growth of the coralline algae
(Rhodophyta). Phycologia 16:125-131.

Davies, P.S. 1984. The role of zooxanthellae in the nutritional
requirements of Pocillopora eydouxi. CoralReefs (1984)2:181-186.

Littler, D., Littler, M.M., Bucher, K.E. and J.N. Norris. 1989.
Marine Plants of the Caribbean: A Field Guide from Florida to
Brazil. Smithsonian Inst. Press, Washington, D.C.

Lobban, C.S., Harrison, P.J. and M. Duncan 1985. The Physiological
Ecology of Seaweeds. Cambridge University Press.

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

Murray, S.N. and M.M. Littler. 1978. Patterns of algal succession in
a perturbated marine intertidal community. J. Phycol. 14:506-512.

Siddall, S.E. 1988. Evaluation if inorganic conditioning of
biological filters using the Aqua Module. FAMA 11(3):4-13, 110-112.

Sprung, J. 1989. Reef Notes. FAMA 12(4):4-6.

Wilkens, P. and J. Birkholz 1986. Niedere Tiere: Rohen-, Leder- und
Hornkorallen. Englebert Pfriem Verlag.