Seafriends Aquariums

Seafriends marine ecosystem aquariums

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)
detailed description and design: inside eight tanks the main habitats of around Leigh are maintained and simulated. (12 pages)
description of potential species: an annotated list of temperate marine species and their habits, by habitat type. (9 pages)

where - snorkel/dive - hire prices - safety suits - sea conditions - Goat Island - café - aquariums - schools

-- Seafriends home -- Seafriends centre -- Rev 20091017,

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 opening.

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 area.
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 them.

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.