The Seafriends temperate marine ecosystem
aquariums are perhaps unique in the world, based on established ecological
principles and new ecological discoveries made here at Seafriends. The
sea water does not return to the sea (as it does everywhere else) but circulates
forever within the glass walls of this ocean ecosystem. Fish are fed but
their wastes eventually become food for those organisms that cannot be
fed: sponges, seasquirts, clams, grazing snails and others. This page describes
how it works.
early beginnings: how the Seafriends
aquariums began and what they are now. (on this page)
Early beginnings The establishment of Seafriends dates back to 1990, even though the
centre opened in November 1992. Knowing that the aquariums would take some
time to settle in, they were the first to be built, about six months before
A marine education centre simply needs to have marine aquariums. However,
for us, located some 80 metres above sea level and some 1000 metres from
the nearest shore, this became an almost impossible task. We knew that
we wanted the aquariums to look like the real sea, so each of the 8 tanks
became dedicated to a particular marine habitat. In this manner the species
that are used to living together, would be kept together, thereby reducing
conflicts of predation and competition. Amazingly, these aquariums house
over 100 different species!
Pure sunlight was admitted to 6 out of 8 tanks, the remaining two dedicated
to deep water habitat which is dark anyway. Two tanks are dedicated to
the estuarine habitat, the sand flats and the mud flats. For each habitat
tank, the sand, the rocks, plants and animals of that habitat were collected
and arranged in such a way as to maximise space, individual territory and
niches. A visitor will find the following habitats:
the mud flats: muddy sand with some rocks encrusted with oysters.
Young mangrove trees, Neptune's necklace weed, mud crabs and many other
inhabitants of the mud flats.
the sand flats: clean sand with some rocks hiding snapping shrimps.
Shrimps, hermit crabs, cushion stars, cockles and many other inhabitants
of the sand flats, including common triplefins and sand gobies.
the deep estuary: rocks and coarse sand with meatball sponges (Aaptos)
and sea squirts. Creatures of the current channels: short-fin eel, parore,
spotty, estuarine triplefin, rockfish, cushion stars, mussels, hermit crabs,
various grazing snails and more.
the sheltered reef: a fragile environment with a large variety of
seaweed, triplefins, camouflage crabs, grazers, sea cucumbers and much
more. We used to keep sea horses but they have become extinct from our
the exposed reef: split into two tanks for the small and the larger
fishes. A variety of sturdy seaweeds, sponges, sea cucumber, snapper, sweep,
spotty, sea urchin and more.
the deep reef: a growing variety of sponges, sponge crab, hermit
crabs, sand stars, shrimps and more.
the 'sin bin': a growing variety of anemones, hermit crabs, ambush
star, prickly star, scorpionfish and more.
Already from the very beginning, we knew that pure sunlight would be important,
even though requiring more maintenance (cleaning windows). It allows phytoplankton
to grow from nutrients produced by decomposer bacteria. This phytoplankton
could be caught on sponge filters and removed from the aquariums. Yet even
so, frequent refreshing with new seawater was necessary.
But in 2003 we discovered that the planktonic bacteria in the sea had
been overlooked by the scientific world, which we could amply demonstrate
in 2005, by a new plankton method (the DDA).
Further research led to the discovery of some of the most important ecological
principles. With this new insight we could measure that our aquariums were
very unhealthy (as is the sea outside). We also discovered how to improve
In May 2008 the aquariums were refurbished to allow more natural light,
resulting in a major improvement. Yet another year would be required to
grow enough seaweed to reduce infectious bacteria in the water and to create
a healthy environment.
We are looking forward to the next few years, necessary to prove that
our concept of a fully recycling temperate marine ecosystem, is really
working. For now, these aquariums are unique in the world.
0811050: Nov 2008: immediately after letting more light in,
the four year old sea rimu began to grow and sponges showed signs of health.
But nearly a year would be required to have enough seaweeds to benefit
all tanks. In the foreground round Aaptos sponges and a yellow nipplesponge.
Note the natural sunlight.
0910048: Oct 2009: the sea rimu and an unidentified red seaweed
grew prolifically, and the time has arrived to try young ecklonia (top
right), sargassum (bottom left) and a fragile red seaweed (centre). Note
the growth rings on the large greenlipped mussels (bottom right). Several
buckets of seaweed have in the meantime been harvested. Notice the natural
sunlight. We're going into spring now.