Management of closed-system marine aquariums
© Biologischen Anstalt Helgoland 1970
1. The major changes which take place in a captive body of sea water include decreases in alkaline reserve, pH, and dissolved oxygen. Inorganic nitrogen compounds, carbon dioxide, phosphates, dissolved organic compounds and bacteria increase in concentration.
2. Methods which have been applied to reduce the rates of these changes in semiclosed systems include buffers, nitrification by bacteria, ozonation, ion-exchange resins, protein foaming, ultraviolet light, microfiltration and dilution of the culture medium.
3. Design criteria for a basic culture system include, forOctopus bimaculatus: (a) 500 liters of medium per kg of animal; (b) a 0.1 m3 filter bed consisting of 2–5 mm grains of magnesium — bearing calcium carbonate; (c) a flow rate of 80 l per m2 of filter bed per min; and (d) replacement of 25% of the culture medium per month.
4. Similar systems will support heavier loads of hardier animals, e.g. up to 7 kg ofHomarus americanus.