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On Saturday the 6th of August the Marine Aquarium Society of Victoria had a guided tour of behind the scenes at Melbourne Aquarium. Such a tour really opens up a hobbyist's eye to the challenges involved in maintain such a large system.

Oceanarium Filtration

The oceanarium is HUGE and all of that water needs to be constantly circulated and filtered. Not a trivial task. The two images below show the appearence of the tank from the top. Can be seen is the glass bottomed boat and a dump bucket used for water circulation in the back ground.

Oceanarium top view.

Oceanarium another top view.

Two large trickle filters which are about 5 feet tall are used for the biological filtration. a top view of one of them shown in the image below.

Oceanarium trickle filters, top view of one.

To maintain water quality and clarity ozone is run on most of the tanks, including the main aquarium. And this does require a decently sized ozone generator! Since ozone is being used, then the ORP on the tanks is monitored constantly. The risk is that residual bromine generated by the ozone when maintained at too higher levels causes serious gill damage to the fish.

Oceanarium ozone generator.

Ozone generator air cooler.

With the significant number of tanks, large volume of water and pieces of equipment, there is bits of plumbing running absolutely everywhere.

Small sand filters.

The company the supplied the equipment is Aquionics, most likely design and installation as well.

Equipment supplier for the filtration.

The water quality of all tanks is monitored on a daily basis. Some tanks has continuous displays like the one below. However, on this particular instrument only the top reading, for ORP, is actually correct. The oceanarium's pH runs at around 7.9.

Oceanarium parameter readings (only ORP is correct reading).

A major issue with maintaining such a large volume of water and livestock density is the pH. In order to keep the pH caustic soda (sodium hydroxide, NaOH) is dosed overnight.

Caustic soda dosing drums for pH control of oceanarium.

Caustic soda used for pH control of oceanarium.

And the other major issue with a large bioload is the nitrate levels. For some time the levels had been on the rise then one of the curators started to play with some denitrators. They appear to be having an influence, with the nitrate concentration falling.

Oceanarium denitrators.

Sugar dosing/feeding pump to the oceanarium denitrators.

Biolgical filtration of the water is provided by a number of large sand filters. These are regularly backwashed to keep them clean.

Oceanarium large sand filters and protein skimmer.

Oceanarium large sand filters.

Eight very large protein skimmers are then used for maintaining the water quality of the tank. Not sure how many were in operation at the time, but pretty sure that it wasn't all eight, with two seemingly not in operation. They are located on the level below the top of the tank, with the collection cups protruding up to that level.

Oceanarium protein skimmer.

Oceanarium protein skimmer foam riser.

2 inch venturi valve operating the large protein skimmers.

Oceanarium protein skimmer feed pump.

A major design flaw with the filtration is that the protein skimmers are actually located beside the tank. So the water cannot drain via gravity correctly, but there isn't anything that can be done about that now.

Oceanarium protein skimmer collection cup.

Oceanarium protein skimmer foam production.

Oceanarium protein skimmer foam production.

The top of each collection cup contains a number of water nozzles that are used to wash/clean the collection cups. And with all of those protein skimmers in operation a large amount of skimate is generated. The tank below had approximately 300 litres of skimate in it.

Oceanarium protein skimmer collection cup cleaner.

Oceanarium protein skimmer skimate collection tank.

Jellyfish Tank

A number of the species kept are temperate, so the water has to be cooled to the correct temperature range.

Chillers for jellyfish tanks.

Coral Atoll Tank

This is the large cylindrical tank next to the entrance foyer and cafe. Filtration is provided by two large protein skimmers (not as large as the ones on the main tank) and two trickle filters.

Coral atoll tank protein skimmers.

Coral atoll tank protein skimmer venturi valves.

Coral atoll tank protein skimmer collection cup.

Coral atoll tank trickle filters.

Coral atoll tank ozone controller and meter.

BHP Tank

This has to be double checked, but this protein skimmer was operating on the BHP tank.

Protein skimmer venturi valves.

Protein skimmer collection cup for BHP tank.

Cuttlefish Tank

Only a small protein skimmer was operating on the cuttlefish tank. Nothing large is probably required due to the low bioload in the tank.

Cuttlefish tank protein skimmer (Aquasonic?).

Coral Tank

The tropical coral reef tank was lit by 5 (?) 400 W metal halides. Due to the depth of the tank, they would possibly step up to 1000 W lights at the front on the tank. But the 400 W are more than sufficient for the back sections of the tank which have the reef structure up close to the water surface.

This tank was originally operating two algae turf scrubbers. However, the algae turf scrubbers were disconnect as they were having significant issues with high phosphate levels. It was reported by another public aquarium that it may be due to the algae turf scrubber and since disconnecting the phosphate levels have dropped some. However, it may be that they were not harvesting the algae regularly enough (every 2-3 weeks).

Coral tank protein skimmer (in house produced) collection cup.

Temperate tank

This is the protein skimmer that is running on the small temperate marine tank holding fish such as leather jackets. The blue to the right is the top of the tank and the black tub on the top left of the photo may be a disconnected algae turf scrubber?

Temperate tank protein skimmer (DB ReefTech).

Temperate tank protein skimmer (DB ReefTech) collection cup.

In the words of the tour guide Di, this protein skimmer "works very well", along with the in house one made for the coral tank.

Temperate tank protein skimmer (DB ReefTech) base.

Holding Tanks

There is a significant number of holding tanks behind the scenes. They are for storage, quarantining of organisms, treatment and general holding of livestock.

Upside down jellyfish.

Shark egg tank.