Reader please note that the new management discontinued and demolished these seawater aquariums in 2014.
This page remains active for historical record.
Seafriends Aquariums
describing the Seafriends marine aquariums
By Dr J Floor Anthoni (2005)
The Seafriends marine aquariums are a fully self-circulating ecosystem, in operation since 1992. They have been important for educating visiting students but even more so for the author to learn about the sea, species behaviour and marine ecosystems. In 2004 these aquariums experienced serious degradation which was not understood and could not be remedied until the Dark Decay Assay method pinpointed what was really wrong. Since March 2005 these aquariums have been managed to prograde, thereby offering a glimpse of degradation in reverse and how this manifests itself. This document describes the aquarium system and the ideas behind it.
Introduction to the ideas and principles behind these aquariums: self-circulation, constant volume, cooling, oxygen supply, isolated habitats, tidal tanks and more. 
Design of the circulation system, aquariums, dimensions and other considerations. Where improvements can be made.
The main habitats around Leigh: estuarine habitats, reef habitats and the 'sin bin' with predators.
Methods of quality control and maintenance
What went wrong and why flushing with new sea water did not help.
By keeping track of water quality with the DDA method, the health of the aquariums improves gradually. At the same time new animals and plants are introduced to stock the aquariums such that they maintain ecosystem health.
major improvement In May 2008 the amount of incident sunlight was more than doubled by a simple modification to the roof and hoods. A new era began.
A timeline of progress in progradation, symptoms and new species introduced, with photos. (in progress)
An annotated species list by habitat type. A separate document (9 pages)
For comments and suggestions, please e-mail the author, Dr Floor Anthoni
-- Seafriends home -- DDA index -- site map -- Rev 20050623,20061115,

One of the first things built for the Seafriends Field Centre were the aquariums because we knew that they needed quite some time to settle in. Indeed the first six months gave many problems. There was only little money available (NZ$16,000 from own savings) such that we had to achieve the most for the least expense. Temperate aquarium ecosystems are not common around the world and when we enquired around, the firm advice we were given was: "Don't do it!". But what is a marine education centre without aquariums?
We then realised that the whole venture had to be done by the seat of one's pants, in full ignorance. We decided on six tanks of 600 litres each, measuring only 60cm high to make do with 10mm thick glass and to be able to maintain it from the outside. The tanks were to be raised to eye level, convenient for teenagers to adults but youngsters had to stand on beer crates to peep in.

We decided we would need one tank for each habitat or habitat zone and we were not certain about estuarine tanks. These mainly show sandy and muddy bottom and would be less interesting than the others. But then we realised that we were doing all this based on ignorance, meaning that they should be there because we could not predict their role in the whole. All habitats were to be interconnected by their shared outlets and inlets.

So the tidal tanks were built. As it turned out, children find these the most fascinating with their hermit crabs, cushion stars and other creatures. We simulated the tide on a strict twelve hour cycle, the mud flats inundated for only four hours (because they are higher up the estuary) and the sand flats for eight hours every twelve hours (later this became 6/6). The creatures didn't seem to mind that the moon cycle was not simulated fully. The tidal movement was achieved with two circulation pumps in each tank, pumping the water out to the other, controlled by an electrical time clock.

As we aimed for a fully operational ecosystem, we had to let sunlight in from above. Fortunately the roof of the lean-to shed where once sheep were dried overnight before being shorn, was low and covered in corrugated iron which could easily be removed and replaced with transparent corrugated Lexan (polycarbonate). The shape of the roof forced us to align the tanks east to west rather than north to south which would have allowed for more light. With the knowledge we have today, this was a mistake as the density of life in these tanks is entirely determined by the amount of sunlight they get.
We chose not to have powerful electric lights as these run up a high electricity bill, and the heat they produce must be compensated for by a more powerful cooling system, also a financial liability. It so happens that sunlight is the coolest light available, and is (still) entirely free of charge. All aquariums have lights but these are operated with a PIR (passive infra-red) presence switch whenever people enter the room.

The tanks were designed such that the water could circulate in a natural way, entering from below as cool water and exiting over a weir (dam of glass). Proteins from wastes would collect at the surface and be skimmed over the weir towards the shared bacterial 'filter'. The other function of the weir is to keep the volume of the aquariums at a constant level, such that we would know precisely up to where to replenish evaporated water with fresh. It also provides a safety against tanks draining in case of an accident.

The bacterial filter contains hollow Siporax beads (expensive but lasting) over which the water flows. It is cooled by a cheap (second-hand) air conditioner which also cools the room. Part of the air blows downward with the flowing water over the Siporax beads which oxygenates and cools the water within seconds but also contributes to evaporation. In winter the air conditioner is turned off and air circulation over the filter is maintained by the flow of water. The bacterial filter does not 'filter' anything. A large load of bacteria inside the filter converts what it is able to in an environment rich in oxygen but kept entirely in darkness. (Later an in-line water cooler was installed)

From the filter, the water ends up in the sump from where it is pumped up by a spa (jacuzi) pump. The pump forces water at high pressure through the pipes, thereby keeping the inlet pipes free from marine fouling, a serious problem in marine aquarium systems. The returning water flows under low pressure, thereby fouling the outlet pipes in a matter of months. Thus a third set of pipes is kept fallow and sealed such that all life inside dies and decomposes to a stinking mess. When this pipe is needed, the black putrid water is pumped out to a wastewater tank and pipes are swapped by means of flexible radiator hoses.
The aquarium ecosystemThe Seafriends aquariums are run as an 'open' ecosystem because some feeding occurs as the aquarium cannot sustain predator species. But adding food to the ecosystem will eventually result in very high nutrient loads and eutrophy the system. Thus excess nutrients need to be removed. In commercial aquarium systems this happens by pumping new seawater through, something we can't do, located 1.5km away from the sea and at 150m altitude. The diagram shows how we solved this. Above the separating line a normal aquarium is shown or tanks with fish as we call it. Fish are fed and soil their water, but the water is pumped out, often at the rate of eight refreshments per day.
In our ecosystem aquaria we have bacteria inside the bacterial filter but at least as much outside on the glass and in the sand. These bacteria convert feces and urine and dead matter into nutrients. By admitting light, the nutrients cause phytoplankton to grow, which is consumed by filterfeeding clams and sponges. The nutrients also make stringy algae grow on every object in the aquariums, and these are grazed by grazing snails. When the aquarium is healthy, it also produces some zooplankton.
One of the largest plankton catchers are our sponge filters which circulate water through a foam pad, thereby trapping dirt, phytoplankton and bacteria. Once a week (less frequent in winter) these foam filters are washed and the washwater discarded. In this manner we remove wastes from the aquariums without replacing the water.

The Seafriends aquariums are unique in their kind as a fully functional open ecosystem that uses the phenomenal growth of plankton to remove wastes.

We keep a pulse on the aquariums by monitoring the levels of the most poisonous intermediary products: ammonia, nitrite and nitrate. Once the aquariums have reached stability, the ecosystem has also become very sturdy, surviving pump failures and prolonged power breaks. But even though seemingly stable, the aquariums can become sick. We are watching the marine creatures carefully as they exhibit the first signs of stress.

The ecosystem can become unstable because of overfeeding or by an accident such as a pump failure. When necessary, new seawater is obtained in a 600 litre black polythene tank on a trailer and old seawater returned to the sea. Until recently, this solved most of the unexpected problems. However, in 2004 when the aquariums became really sick and even sea cucumbers died, the refresh cycle no longer delivered. What was wrong?

The Dark Decay Assay method invented by Dr Anthoni to measure the health of natural water, came just in time and it showed us not only that the aquariums were at a level of health comparable to the worst found along our coasts, but also that the sea around Leigh has become too sick to be of any use for refreshing aquariums with. Then the idea arose to nurse the aquariums back to health (progradation) using the new-found knowledge with the DDA method. It should be possible to end up with sea water healthier than that found inside the Goat Island marine reserve. Thus the Seafriends aquariums became a scientific tool for studying marine degradation by the reverse process of progradation. It is a very exciting prospect.
HOWEVER, In 2014 the aquariums became very sick and most creatures died. It was later discovered that the seawater from the Whangateau Harbour was no longer suitable. It also caused mass mortality of shellfish in the harbour.
The new management then decided to abandon these aquariums, thereby also saving on maintenance and electricity.

aquarium setupThe aquarium system was designed for utmost simplicity using materials that are easy to obtain, so that maintenance can be done locally. The tanks, measuring 120 x 60 x 60 cm were placed on sturdy wooden tables, connected by a hood to the roof. One corrugated iron roof sheet was removed and replaced with a transparent Lexan corrugated sheet. The pipes were placed underground in a sand matrix covered by garden tiles. The tops of the aquariums were enclosed in a plywood hood whose inside was lined with silvered building paper. The aquariums could be reached through flap doors of 30cm high between the glass and the hood. This is enough to place one's head inside, to reach the bottom everywhere and to pass small buckets through. The flap doors are covered in information sheets.

aquarium designThe aquariums are all at the same level, about 120cm above the floor and the sump tank is located about 40cm below ground level, such that water flows swiftly back to the sump. in the weirs there exists ample head of water to remove bubbles and air locks. A spa pump sucks water out of the sump and pumps it under high pressure through a non-return valve to all tanks. Here it enters close to the bottom and exits over a glass weir along the surface. The small triangular basin behind the weir fills and empties as the pump works intermittently, affording enough pressure to overcome any air locks. Above the sump is a dark box filled with SIPORAX glass beads that have very fine tunnels for bacteria to settle on but their open cores allow the water to flow through swiftly. A standard air conditioner blows cool air into the aquarium room and this flow is tapped to also flow through the box. By allowing air to enter, the water is oxygenated almost instantaneously. Since August 2008 when the roof was opened up further to let more light in, an in-line Haylea water cooler of 1kW has been installed.

The whole idea behind the Seafriends aquariums is to afford visitors a look at the local sea in miniature. So all habitats and habitat zones needed to be represented.

Mud flats
The mud flats are found in the estuary where shelter is found from wind. Here the fine mud from the run-off from the land can settle out. In the north of New Zealand one finds the mangrove tree here (Avicennia marina resinifera). Since the fine mud is mixed with bacteria, benthic (bottom) algae and detritus from plankton, it is edible to a number of organisms. One finds the mud crab here and many grazing snails among which the mud snail is rather unique. By means of small circulation pumps controlled by a time clock, we simulate the tide by pumping the water in for four hours out of twelve. 

Sand flats
Where the estuary encounters wind, small waves are produced and these winnow the mud from the sand, allowing it to be transported out to sea. So the bottom is sandy. One can find eelgrass in the upper reaches of the estuary and various clams in the lower reaches. A number of crabs, hermit crabs, snails and cushion stars are found here. The tide clock and small pumps pump the water in for eight hours out of twelve.
Note that the two tidal tanks do not take part in the overall circulation as much as the six others. The supply pipe has been quenched (made much smaller) for them to remain almost independent. As a result, their water is not cooled and allowed to go through extremes. This in turn allows plankton to grow much faster than in the other tanks. The sandflats furthermore reflect the sunlight and almost doubles the amount of light experienced by plankton. They have become our main phytoplankton suppliers. This was important for the survival of oysters.
Deep estuary
The deep estuary is marked by current channels. It never falls dry during spring tides. Because of its shelter against ocean waves, currents and rich waters, it is rather distinctive with various seaweeds, filter feeders, shellfish and starfish.

Sheltered reef
The sheltered reef is not very common, as it is connected to the open sea but sheltered from the brunt of ocean waves by a promontory, inlet or similar feature. It is an area rich in variety, particularly of fragile species. One finds a large number of fine seaweeds there and many representatives of all phyla. Unfortunately people like to live near such places, reason that this habitat is threatened everywhere.

Exposed reef
The exposed reef covers the sun-lit zone of the rocky reefs around New Zealand. Around Leigh it is bordered by stringy bladder kelps on top and the stalked kelp forest lower down. In between one finds a barren zone grazed by sea urchins. This habitat zone is rich in species. In our aquariums we cannot simulate the wave action and bright sunlight, and this limits what the tank can show.

Deep reef
The deep reef extends below the photic (sunlit) zone such that plants can no longer grow for lack of light. One finds a variety of filterfeeders here such as various clams, sponges and seasquirts. Also detritus feeders are found. We placed the deep reef under dim light to simulate the light situation. Electric torches by all tanks allow visitors to see into dark spaces.

Sin Bin
The Sin Bin is not a habitat found in nature but a tank that allows us to keep animals that are particularly destructive in the habitat where they belong. The large anemones are fierce predators, catching snails, crabs, sea horses and so on. The dwarf scorpionfish is also quite destructive, and predating starfish such as the eleven-armed star and the ambush star. Even so, we had to ban the most destructive of all, the predating conches and the seven-armed star. Some crabs are very destructive like the paddle crab of the sand flats and also the spiny lobster (crayfish) and the octopus. They practically need a tank for themselves with a few animals that they leave alone (but crayfish eat everything).
We discovered a natural habitat with many of the creatures of the Sin Bin in the interface between a long sandy beach and the first rocky outcrops of a bordering rocky coast. During storms clams and other animals are washed up on the beach and depending on wave direction, are gradually washed to the rocky outcrops. Here they become trapped in the gullies and in the deeper reaches. Thus food occurs in abundance with long periods of scarcity in between. This Shell Trap habitat is inhabited by organisms able to live from binge to famine, such as anemones, sea stars and several predating conchs. Not all clams die during the wash-up as they are able to settle in the deeper regions, where octopus abound.
Quarantine tank
The quarantine tank is placed above the sump, connected in a side loop. It serves as a temporary holding tank for sick or stressed animals and it also serves as a learning place for slow-feeding fish that have to adapt to our food. It also allows new fishes to adapt to the four walls and that there is no escape. Dubious predators such as some conchs and crabs are placed here to observe what damage they can cause.
The quarantine tank also serves to monitor water flow as it is filled by the sump pump but emptied by a constant flow. A flow switch sits in the outlet pipe. When the flow is too low, a resettable timer expires, ringing the circulation alarm and an alarm monitoring service.

In nature predation is not well defined, as we discovered. Basically any larger fish eats any smaller one. So we have to keep a watchful eye out for size. Fortunately our aquariums are too small to accommodate large fish (say larger than 20cm), and these are returned to the sea as soon as they become a menace to others or when they require too much food.We discovered that most fish can be restricted in size by not feeding them too much. These "bonzai" fish stay small in size, yet mature. Because they survived previous disasters and diseases, they have also become very resistant to disease.

Aquariums require maintenance because they are such small environments and are usually overstocked. Services provided by nature such as circulation, oxygenation, warming, cooling, wave action and waste removal must be provided artificially. In order to understand this better, we'll discuss the five basic kinds of aquarium system.

Public marine aquariums
Public marine aquariums want to show the public a large collection of remarkable species with the least amount of problems or risks. They are usually located at the sea side where water can be pumped in from the sea and out again. An underground sand bed helps to filter the incoming water. It is then sterilised by ultraviolet light to kill all bacteria. The refreshment rate is high, about eight times per day. 
Such aquariums often have Perspex transparent tunnels which are easily scratched while cleaning. So the rate of fouling is kept to a minimum by dim lighting. These aquariums are not self-sustaining ecosystems and are unsuitable for plants and lower organisms such as sponges.

Commercial marine fish tanks
For holding and transporting live fish, commercial tanks have a minimum of life-support. Most commercial fish species are rather hardy, able to survive a few weeks in very poor conditions. Life support consists essentially of oxygenation, cooling and circulation. No bacterial filtering is applied. Sometimes an ultraviolet light steriliser is provided. Freshwater fish like carp and tilapia are hardier still.

Tropical fresh water aquariums
Keeping a tropical freshwater aquarium is very popular because it is not difficult. The only things needed are warming, circulation and filtering for waste removal. Most freshwater fish species are very hardy and lazy, requiring the least amounts of food. Many fish also adapt to the poor quality water, being able to survive for years. Maintenance also consists of replacing the water periodically and this could be a problem since drinking water is often chlorinated and fluoridated. However, every dwelling can collect enough rain water. But when an unknown limit is exceeded, things can go wrong rapidly. Also diseases can be introduced from various fish vendors.

Tropical marine aquariums
The tropical marine aquarium is popular because of the sheer variety of beautiful and weird species that can be kept, from corals to anemones, crabs and snails to starfish and many gaudily coloured fish species. But marine species are not as hardy as freshwater ones, and this brings problems. Because the tropical water is warmer than the ambient temperature, only warming is required, which is much easier than cooling. These aquariums must provide for heating, circulation and filtering for wastes. Often very strong lights are provided to enable corals to grow. Some ultraviolet-A light can accentuate fluorescent colours. An ultraviolet-C steriliser is strongly recommended to remove bacteria from the water. At times the water must be replaced to remove liquid wastes, and this can be done by dissolving sea salt in clean fresh water.

Temperate marine aquariums
Temperate marine aquariums are more difficult than tropical ones, not only because a form of cooling must be provided but also because temperate species are rather energetic, requiring a high food intake. Apart from this, they can be managed like tropical marine aquariums.

Temperate marine ecosystem
The most difficult to keep are marine ecosystems. An ecosystem is essentially self-sustaining, requiring neither feeding nor waste disposal. All minerals, nutrients, oxygen and carbondioxide are circulated within. It can essentially be capped and live forever, as long as circulation and cooling are provided. However, such complete ecosystems are rather boring for the public since they need to be very large to accommodate predator fish species. Their density of life is much less than that along the coast because they do not have an extra supply of plankton. For this reason, the Seafriends 'open' marine ecosystem is supplied with food for interesting species, and their wastes are converted to phytoplankton which is partly removed by filters. There exists a large commercial market for materials and species.

Window cleaning
Because the sunlight is allowed in and the density of life depends on how much light can be admitted, the aquarium windows are always subjected to rapid growth of hairy algae. The many grazing snails do an excellent job, cutting window maintenance by more than half, but regular scraping is still required. Gradually very hardy algae like pink paint with limestone 'leaves' take over and the windows need to be scraped clean with a sharp paint scraper, without scratching the glass.
Circulation and oxygenation
Circulation and oxygenation are important, but since each tank has ample plankton, micro algae and macro algae, and a supply of light, most oxygen is produced inside each tank. During a bright day one can see oxygen bubbles escaping as a sign of complete oxygenation. The fixed-volume design with weirs and two tidal tanks also with constant volume, causes the circulation to stop rather quickly as water evaporates and the small excess volume kept in the weirs, becomes nil. Thus part of the daily routine is to check circulation. Depending on temperature and humidity, the 3000 litre tank volume needs to be topped up with several buckets of fresh water each week. For this we are now using rain water, as bore water and spring water contain too many minerals and nutrients.
We can not use ultraviolet sterilisers because it would also kill the phytoplankton, so necessary for all filterfeeders and for removing wastes. This makes a marine ecosystem a tricky operation.
Waste removal
Waste removal is the most important task as the health of the water depends entirely on it. Filter sponges are rinsed weekly and the waste water discarded. We are still experimenting with the best ways of doing this. It would be ideal if the organisms in the tanks would remove all excess plankton and nutrients, but even in an ideal situation, this would not be enough.
Depending on temperature, each tank needs a minimum of food to keep those organisms that need it, happy. Thus feeding judiciously is as important as waste removal. Every organism is watched for signs of health or discomfort, because such signs show long before they can be measured.
Quality control
Water quality is tested regularly for ammonia, nitrite and nitrate content but since the invention of the Dark Decay Assay (DDA), we have a much better measure of water quality. During the period that we are prograding the aquariums, the DDA is done fortnightly to monthly. Since the aquariums have settled within healthy boundaries, measured with the DDA, ammonia, nitrite and nitrate levels have been perfect. Over time also pH increased slowly from a low 7.9 to 8.2 but note that pH levels fluctuate seasonally.

Degradation in the sea happens invisibly and slowly, alternating with the El Niño cycle, such that most people remain unaware. In the aquarium ecosystem it happens when feeding exceeds waste removal. Conversely, progradation can be achieved by removing more wastes than that caused by feeding. Most marine aquariums are somewhat stressed, and we have run our aquariums in a rather stressed mode in order to show more interesting creatures like an octopus. As a result, bacterial levels remained too high for certain organisms, but without DDA one does not know this. A large and active bacterial component is absolutely necessary for any ecosystem, but the decomposers need to be locked up inside the sand, a filter and so on, and should not be allowed to roam free in the water. 

Doomsday came in the year 2004 when problems in our aquariums could no longer be cured by replacing the water with new sea water. We had not noticed two main causes:

  1. The sea around Leigh had become eutrophied, with nutrients and plankton densities near the maximum possible. The DDA method showed this in March 2005. Sea water may improve somewhat in the La Niña phase from 2006-2008 but that is still not a good prospect.
  2. We have been using bore water as our rain water supply runs out in summer. The DDA has shown that this water has a high level of nutrients and minerals. We have now installed a small rainwater tank solely for the aquariums.
At the all-time depth, our aquariums were plagued by 'brown slime' (Ostreopsis, a very posionous dinoflagellate scum) and poisonous stringy algae (cyano bacteria of all kind). Cleaning just spread it further. At this stage the rather hardy sea cucumbers died and most grazers like snails and sea urchins. Already other organisms like anemones, the octopus and snake stars showed serious signs of stress. So urgent action was necessary.

We removed all large animals, including octopus and crayfish and all stressed animals since their deaths would contribute to the problems. Then we discovered that cushion stars were impervious to cyanobacterial poisons, and we let many of these clean up the mess. It worked, as we also at the same time aggressively removed wastes (in the presence of sunlight, nutrients convert to phytoplankton which is caught on standard aquarium sponge filters and removed weekly).

As more and more nutrients were removed, paradoxically, the algae grew faster and faster, and so did the wastes we removed. Then we discovered the DDA and applied it to the aquarium water. How had we been able to run this aquarium with such poor quality water for so long, and without DDA? And why did this not show up in the levels of ammonia, nitrite and nitrate? Obviously the DDA is a far better quality test.

We have never been able to grow marine macroalgae like the brown, green and red seaweeds, but never found an acceptable explanation. We tried all possibilities such as more or less sunlight, trying sea weeds from various depths, making strong currents and even wave action, but nothing seemed to help. Now we know that seaweeds are rather sensitive to bacterial attack.

Progradation, the way forward
Armed with new knowledge about how the marine ecosystem really works, we are now prograding the aquariums by a different approach. In the past we focussed on healthy bacteria to decompose all wastes but now we have changed our priority.
There are plenty of bacteria in the system. They work best when attached or locked up inside the bacterial filter, the sand and even the waste removal sponges. But they must not be allowed to roam freely. This makes cleaning the sand, for instance a tricky operation which must not be done too often and with much care as well. (We have now stopped doing so)

Our first priority is now to create an environment where plants are happy (forget about fish for a moment). Once they grow, they will remove nutrients from the water and create a bacterial medium in their slime that helps decomposition while at the same time helping other plants grow and trapping free roaming bacteria. We expect that this will make an enormous difference as also phytoplankton are plants.

We are now (June 2005) at a stage that filter feeders like mussels, cockles and even seasquirts and sponges are growing. They too remove wastes from the water. Once growth is sufficiently fast, we will stock larger numbers of these and try other varieties.

By now the aquariums look quite different from what they were before, as more and more organisms take over from the waste filter as the waste filters are already becoming less effective. We expect that their combined synergy leads to the final phase, as we hope to be able to also nurse the plankton ecosystem to optimal health.

Within this plant- and filterfeeder- dominated environment, we then plan to stock a tolerable number of fish and perhaps some energetic ones like trevally.

The process of progradation will enable us to learn more about degradation and how the various species react. The Seafriends marine aquariums have thus become an important link in our research.
aquarium progradationThe graphs show how the aquariums are prograding. In black the total biodensity (slush + decomposable biodensity), in green the decomposable biodensity and in red the bacterial rate of attack. After very high values before April 2005, bacterial activity (ROA) gradually decreased from 30-40 hion to below 10 hion. Above 15 hion, most seaweeds are not able to survive. In December the water was so clean that mussels could not find enough food. In March-April 2006 excessive stocking allowed the water to degrade to a peak level during which young snapper died. Progradation was applied aggressively in May and June 2006, with ultra clean water as result.  The ROA peak in September was due to mussels dying. They have since been shifted to the tidal habitats where plankton densities are kept higher. Also some filter pumps have been disabled. Note how the black curves of total biodensity remain high due to high slush content, but as seaweeds establish themselves, it is expected that this source of nutrients will be utilised. In October 2006 various green, brown and red seaweeds were growing happily, as also a large variety of sponges did.
Ideally the green line should stay on or above 100 hion and the red line below 10, in order to simulate a healthy coastal sea. Ideally, the various tanks should be managed in three groups: estuarine (dense plankton), near-coastal and far-coastal (cleanest water). Please note that very little is known about these aspects of the sea and how the DDA measurements vary seasonally.


sand anemone and olive actinia
0506015: The pink sand dahlia (Bunodactis sp) and olive-green olive actinia (Actinia olivacea) are showing signs of health by being open most of the time and growing slowly. Olive actinias are found in the inner Hauraki Gulf and are rather hardy but most have now disappeared. The red actinia (Actinia tenebrosa), once common above low tide, has disappeared from many places and from our aquariums. June 2005.
White tipped anemones multiplying
05052431: white-tentacled anemones (Actinothoe albocincta) are rather sensitive to bacterial attack but now they are growing and multiplying. May 2005

Common scallop
05052434: the common scallop (Pecten novaezelandiae) feeds on zoo plankton of which there is too little to keep them alive for as long as they can live. Notice the red spot left of centre, which is a growth of a very hard calcareous alga on the aquarium window. May 2005
variable triplefins and pink golfball sponge
0506020: pink golfball sponges (Tethya australis) are growing and multiplying, as also the orange golfball sponge and the meatball sponges (Aaptos spp). Two variable triplefins (Fosterygion varium) have formed a mating pair, having laid a nest of eggs, seen under the female on right. June 2005.

first signs of seaweed growth
0506025: the first signs of seaweed growing were found on the difficult to keep sea rimu. The photo shows how it first began growing roots. The yellow stems belong to stalked kelp, which is neither dying nor growing. June 2005.
Sea rimu growing new sprouts
0506037: Sea rimu growing new sprouts as old branches begin to bud. June 2005. Note that the winter is not conducive to plant growth because of low temperatures and low light levels.

A major improvement
It has always been clear that the amount of sunlight was the aquarium's main limiting factor, and possibly also the main reason why brown seaweeds could not be kept. In order to fix this, the whole aquarium room needed to be re-built from scratch, with wider tanks lined up in a north-south direction and this would cost $120,000 if we did the work ourselves. With Seafriends in a state of near bankruptcy, this was not an option.
Then one night the candle lit: we could achieve most improvement by opening the roof up entirely, lowering the ceiling between the tanks and by placing more reflective material, for a mere $1000! It took only a couple of days to do, and the result was beyond expectation.

Suddenly seaweeds began to grow spontaneously, of which two red seaweeds that we never placed in these tanks. Still, the brown seaweeds did not take. We had discovered that by their symbiotic association with bacteria, seaweeds decompose wastes more effectively than bacteria on their own (symbiotic decomposition). Thereby also the free-floating bacteria become less numerous (losing out in competition), and with it the chance of infection and disease. In other words, as seaweeds take over, the aquariums also become healthier, until one day also brown seaweeds may grow successfully. The first has indeed happened, and very few mortalities have been recorded, and none in the past 6 months, as also sick sponges recovered.

It deserves mentioning that there are four major limitations to our aquariums and for that matter any other marine aquarium:

  1. The limited amount of light as we discussed before. Light must pass from the sky through a narrow funnel to the tanks below, so no matter how technologically sophisticated, this remains a problem.
  2. Tanks have far too much wall for too little water. It is entirely unnatural. To keep larger free-swimming fish, one must therefore have a round tank, such as found in most shark tanks. The glass walls must also be cleaned regularly.
  3. There is far too little water to simulate the beneficial effect of the larger ocean, such as providing phytoplankton and leading wastes away, and even providing wave action. Thus the planktonic bacteria are more so a problem than in the open sea.
  4. Pumps are rather rough with the life in the water. Their shearing action damages zoo plankton. Thus zooplankton will always be insufficient.

Wave action
Terrestrial plants have 'pumps' to pump their liquids around. Their main mechanisms are uplift by capillary action in thin pipes, and evaporation from leaves, which sucks the liquids up. Downward movement is performed mainly by gravity. By contrast, sea plants have none of these mechanisms. Their transport of liquids is done mainly by external water movement which flexes the plant's tissues, thereby 'pumping' liquids around inside (like the human lymph system). Thus for seaweeds to grow, there must be wave action. (not entirely true)

One can think of many ways to make waves, but if the cost of electricity is also taken into account, few solutions remain that are simple, invisible, cheap and reliable. Our solution was a tipping bucket made from half of a 20 litre chlorine container, cut diagonally. The triangular bucket is hinged critically, so that when it is filled by a small pump, will eventually tip to discarge its content completely, thereby creating a surge of water resembling wave action. This tipping bucket is placed above the tanks, and thus remains invisible. This method has proved to be reliable, even though a few times each year, the algae inside need to be removed.

Seafriends aquariums November 2008
0811050: Nov 2008: immediately 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.
Seafriends aquariums October 2009
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. Natural sunlight. We're going into spring now.

Personal disasters
In Jan 2011 our trained staff left suddenly, leading to a staffing crisis. Then in Sep 2011 Dr Anthoni suffered a severe right-brain stroke with left-side paralysis, preventing him from doing 'normal' work. Due to mismanagement, the aquarium ecosystem collapsed with the death of all species. Resilient poisonous slime and hairy algae prevented normal recovery. At this time Seafriends was up for sale, allowing new management to conduct business, which led to complete termination of the aquariums. We wonder if the spirit of Seafriends will ever return.  - end of an era?