The Open Ocean (properly known as the Pelagic Zone) covers a huge part of our planet - together with coastal seas it makes up over seventy percent of the surface. The volume of all this sea water is enormous.
Water Temperature and Chemistry
Such large volumes of water can resist sudden changes of temperature, and the ocean currents regularly bring nutrients up from the deep keeping the chemistry of the all-important surface waters fairly stable. When aquarists attempt to manage miniature marine environments they will always need to resort to specialist equipment and techniques to keep water quality constant (thermostatic heaters, pH control etc.), but maybe some things can be improved by enrolling the help of nature.
Plankton
The top part of the open ocean and coastal seas lets light penetrate to a depth of about 200m maximum (far less in turbid water), allowing plants to photosynthesise. Away from the coast almost all of these plants are microscopic and they feed millions of very small animals (the zooplankton). These planktonic animals feed larger planktonic animals, and so on up to the top ocean predators. Aquarists can never reproduce the ocean in its entirety, but the use of ‘Biotope Tanks’ can go part of the way.
Reef Aquaria
Many marine tanks house tropical fish species that originally lived on coral reefs, and often they also have one or two living corals. Again there is no way that an entire reef can be included, but things are made easier if wise choices are made about exactly which species should be kept together. A good maxim is to restrict the choice of specimens to those found living together in nature, and this has the added advantage that it can lead on to give an extra dimension to the hobby.
Biotoping
Ret Talbot, in a series of articles, discusses how to set up a system of tanks that model, in some respects, the reef environment of a part of the Banda Sea. Earlier articles have looked at the roles of Mangroves and Seagrasses in this ecosystem, but what can hobbyists possibly do to include a little bit of the open ocean in their system?
A Tank for Plankton?
Temperature control and water chemistry will always need to rely on artificial intervention, but maybe some carefully chosen planktonic organisms could be nurtured to help with feeding the fish and recycling the nutrients. The phytoplankton (microscopic plants) would need a good light-source, and the zooplankton (small animals) would be able to feed on the plants and go on themselves to become fish-food. Finding planktonic species that could be maintained together in this way would be a real challenge, and if there are any hobbyists out there who have experience of this sort of thing they could contribute to the discussion, where biotopers are encouraged to share their findings. (See blog).
Other articles by John Blatchford
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