Dutch MiniReefs: An Update
The latest news from the home of the reef aquarium

Articles in this and other publications have dealt with so-called
"European" reef aquariums. After a recent trip to the Netherlands, it
became quite clear to me that there is no such thing as a "European"
reef aquarium. The simple fact is that there are as many different
approaches to reef keeping as there are countries in Europe, or
provinces in the Netherlands. In this article I would like to
describe some of these aquariums and to offer a glimpse at what is
state of the art reef tanks in the Netherlands today.

When George Smit's articles describing the Dutch Minireef aquarium
began appearing in January 1986, the pages included pictures showing
aquariums full of the macroalgae Caulerpa. The importance of
Caulerpa was explained and the various species were
described.

After viewing eight private aquariums, three retail outlets and one
public aquarium, I can tell you that I did not see a single blade of
Caulerpa in any of these aquariums. When I asked about this apparent
discrepancy, I was told that the use of Caulerpa was merely a stage
they had gone through several years ago and very few aquariums no
included it. I was soon to discover that there were various other
"surprises" in store for me during my visit!

While in the Netherlands, I was shown various privately owned
aquariums with the assistance of two gentlemen, Mr. Leen Dekker and
Mr. Tony Achterkamp. Mr. Dekker showed me aquariums in the southern
part of the country near the city of Dordrecht, and Mr. Achterkamp
took me to see three aquariums in the center of the country, near the
city of Apeldoorn. As a result, I saw two different approaches to
keeping aquariums.

I was told that there were yet other approaches, and that the exact
techniques employed really depended on what part of the country you
were in and which "reef clique" of aquarists you were following. For
instance, in the city of Utrecht, many hobbyists were using Phillips
Actinic 03 tubes, whereas very few hobbyists outside the city did so.

My thanks go to these two gentlemen for taking the time to show me
around and for answering my numerous questions. I also extend my
thanks to the owners of the aquariums for opening their homes to me
and for allowing me to take photos of their reef tanks!

The first reef tank I saw was Mr. Dekker's two-year- old aquarium.
The dimensions of the tank are 78 inches x 60 inches x 30 inches,
with a volume of 425 gallons. Filtration consists of a homemade
5-foot protein skimmer and a sump containing a few large pieces of
live rock. Four Tunze Turbelle water pumps are used for circulation
in addition to the main water pump. At the time of my visit, lighting
consisted of six 5-foot, 65-watt Triton fluorescent tubes and five
5-foot, 65-watt Thorn Blue fluorescent tubes. The carbonate hardness
is 10 KH, the pH is 8.2, water temperature is 77 degrees Fahrenheit
and nitrate is 25 milligrams/liter.

Monthly 10-percent water changes are done using natural seawater
collected from inshore seawater marshes. Reverse osmosis water is
used for evaporation losses.

The tank is filled with various specimens of hard and soft corals and
contain approximately 40 fish. What is interesting about this tank is
that other than the live rock the animals were attached to when
purchased, the entire base consists of dead coral skeletons. However,
much of this bare dead coral is covered with growths of
cyanobacteria, (red slime algae) and some hair algae. I will have
more to say about this method after I describe the next two aquariums
I saw, which were set up in a similar manner.

Since my visit, Mr. Dekker has changed his lighting and has replaced
the Tritons with two 120-watt Philips Actinic 03 (the 140-watt
versions of this tube is not available in Holland), two Osram 11
Daylight fluorescents and two Osram 67 fluorescents (intense blue
bulbs). He reported that less than two months after the change, the
tank looked better than ever and the red slime algae had almost
disappeared. Certainly there may be other factors involved in this
change, not just the lighting, but I think the primary fact that
should be stressed here is that the red slime disappeared-for
whatever reason.

The next tank I saw belonged to Mr. T. Broadars. This aquarium was
118 inches x 23 inches x 28 inches, with a volume of 530 gallons.
Lighting consisted of twelve 65-watt Thorn Blue, four 65-watt Triton
and two 36-watt Osram 11 fluorescents. There is an Eheim skimmer, a
trickle filter and a small sump.

This aquarium contains numerous soft corals as well as more than 50
fish, including at least five different species of Pseudanthias,
numerous tangs and surgeons and four specimens of Pseudochromis
fridmani. This aquarium was also set up using dead coral skeletons as
a base. Reverse osmosis water is also used for top-offs and natural
seawater for water changes.

The third tank that Mr. Dekker showed me belongs to Mr. L. Semons.
This aquarium is 78 inches x 43 inches x 31 inches, with a volume of
425 gallons. Lighting consists of four Thorn Blue, two Triton, two
Osram 11 and one Osram 67 fluorescent tubes, all 4 feet long and
rated at 36 watts. In addition, there is a skylight above the tank
that allows natural sunlight to fall onto the aquarium.

Filtration consists of a small 10-gallon sump with a small venturi
skimmer. When I saw it, this aquarium had been set up for six months
and was absolutely packed with hard and soft corals, as well as
numerous Tridacna clams and fish. This aquarium also had a dead coral
base. And. like the other tanks, reverse osmosis water is used to
replace evaporated water and natural seawater is used for water
changes.

It should be noted that all three of these aquariums were designed,
installed and stocked by the same retail outlet. Therefore, they all
share the same design philosophy of using dead coral skeletons
covered with a "veneer" of live corals, and they are all packed with
fish. All three aquariums have a thin layer of white gravel on the
bottom. The gravel is removed and cleaned every two weeks

Criticisms of this method center around the fact that initial losses
of corals and fish are very high and dead animals are merely replaced
with new ones. Also, the selection of some of the fish is
questionable inasmuch as several coral-eating or notoriously
difficult-to-keep fish are included. Nitrates tend to be above 25
milligrams per liter in all three of these tanks. This is most likely
due to the dense fish population, undersized skimmers and/or lack of
substantial quantities of live rock.

At the same time, these aquarists want to have lots of fish and
corals in their aquariums. Unfortunately, they probably go through a
large number of specimens before an appropriate balance is achieved.
Nevertheless, the aquariums are visually stunning!

To be fair, I only saw these aquariums once, in the evening, so it is
almost impossible to make meaningful judgments about the techniques
used. One would need to monitor the progress over several months
before it could be determined how successful this approach is.

The following week, I met Tony Achterkamp and he took me to see three
aquariums that he helped design and install.  Tony believes in the
exclusive use of live rock, and all the tanks I saw contained it. He
also lights the aquariums with a combination of Osram 11 Daylight and
Osram 67 Blue fluorescent lights. These are known as T8 lamps, which
are narrower than the fluorescents common in North America. These
lights are 4 feet long and are rated at 36 watts. An additional
wide-spectrum tube, such as a Triton TruLite, is sometimes added to
give a little warmth to the spectrum, but these tubes are used
sparingly.

Approximately once a year, two or three pieces of live rock are
removed and replaced with new ones. Tony believes that this helps to
introduce new microorganisms and bacteria into the tank. He claims
that significant improvements can be seen in the animals shortly
after this is done.

Filtration for these tanks consists of skimmers and wet/dry filters.
Natural seawater is used for water changes, which are small (less
than 5 percent per month), with either tap or well water being used
for top-offs. These aquariums have been set up for two years or
longer and the growth of coralline algae in some of them is very
impressive. Unfortunately I did not have access to a calcium test kit!

It would have been interesting to measure the levels of elements in
the tanks and the top-off water.  I have a suspicion that the tap and
well water have a high calcium hardness and are rich in other
minerals and trace elements, such as strontium.

The first tank that Tony showed me belonged to Mr. A. Renders. This
aquarium is 118 inches x 30 inches x 30 inches, with a volume of 355
gallons. Lighting consists of two Thorn Blue and 12 Osram 11 Daylight
tubes. All 14 lamps are on together for only two hours.

Nitrate and phosphate measure at 0 milligrams/liter. Water changes
are performed at the rate of about 5 gallons a mont, and tap water is
used for top-offs. The substrate in the aquarium has a depth of
approximately 2 inches.

The tank contains various Amblyeleotris gobies and at least 10 large
serpent starfish to help keep it clean. There are various leather
corals and other soft corals in this two-year-old tank. Some of the
specimens are more than 10 years old and have been transferred from
aquarium to aquarium. One interesting feature is a mated pair of
longnose hawkfish, Oxycirrhitus typus.

The second aquarium I was shown was similar to the previous one. This
one, however, had been running for over five years and some of the
specimens are quite old (more than 15 years) and large. The most
striking feature is the extensive growth of coralline algae on the
live rock, the growth of Xenia and the sheer size of some of the
leather corals. Corals need to be regularly pruned in this tank
because they spread so quickly.

The third aquarium Tony took me to was quite beautiful and had a wide
variety of organisms, including a large tridacnid clam that has
almost tripled its size in some two years. The aquarium is 102 inches
x 28 inches x 25 inches, with a volume of 290 gallons. Twelve
fluorescent lamps are used: seven Osram 11, three 40-watt Thorn Blue
and two 36-watt Triton. A trickle filter and skimmer form the
filtration system. Nitrates are undetectable, the water temperature
is 77 degrees Fahrenheit, KH is 6 and the pH is 8.2. Groundwater is
used for evaporation, and water changes are performed at the rate of
some 50 gallons per month.

The last aquarium I saw during my stay in Holland was that of Mr.
Hank van Stratan. This aquarium is 98 inches x 32 inches x 24 inches,
with a volume of 320 gallons. Filtration consists of a trickle filter
and skimmer. Fourteen 4-foot, 36-watt fluorescent lamps are used:
eight Osram 11, four Philips Special Blue and two TruLites.

Water changes are performed using natural seawater at the rate of
approximately 25 gallons per month. Tap water is used for top-offs.
Nitrates are undetectable, the pH is 8.2, the water temperature is 77
degrees Fahrenheit and the KH is 8.

This aquarium also has live rock and the coralline algae growth is
quite extensive. There are numerous hard and soft corals but not as
many fish as in the aquariums shown to me by Leen Dekker. The most
striking feature of this aquarium is the extensive growth of Xenia
sp. over the rocks and along the back and side glass of the aquarium.

In summary, the reef tanks I saw did nothing to dispel the notion
that the Dutch have very nice aquariums.  One of the striking
differences between the aquariums I have seen in North America and
those in Holland is the greater emphasis on soft corals than on hard
corals-both in stores and in home aquariums. The variety of soft
corals is also definitely greater than in Canada and somewhat greater
than in the U.S.

Why there seems to be an emphasis on the more difficult-to-keep hard
corals in North America is not clear. It certainly cannot be the
retailers or wholesalers.  After all, if people don't buy these
corals, they won't be offered for sale. No, I'm afraid it is the
fault of consumers (hobbyists). As hobbyists, we have to be more
sensitive to environmental issues. Beginners should first master soft
corals, then move on to the more difficult hard corals. Soft corals
have the added benefit of rapid growth and the ability to spread
throughout the aquarium.

There also seemed to be a lack of gadgetry on these aquariums. There
were no redox or pH controllers, no CO2 injectors and very little use
of additives. The simple approach to reef tanks was definitely in
evidence.

I did see one aquarium that had virtually every conceivable device
you could think of, all incorporated into a panel-mounted control
center on the front of the tank stand. This aquarium belonged to an
engineer and as such he loved to tinker with electronics. The tank
itself looked no better than the others, but he definitely derived
more pleasure from his hobby by incorporating his other interests.

Yes, The Dutch still have very nice aquariums, but we are not that
far behind. The North American reef hobby has come a very long way in
the last few years. With an increased understanding of the importance
of maintaining calcium and strontium levels in our aquariums, our
success rate with corals can only get better.