Water changes are performed on a monthly basis and freshwater, passed first through a reverse osmosis unit and then through a deionizing column, is used for topping-off evaporation. A chiller is employed to keep the temperature in the mid-70's. The only additions that John regularly performs, that I am aware of, are fish food and calcium chloride to maintain the calcium level for the corals and calcareous algae. None of the invertebrates are fed directly. The lights come on and go off in stages over a 13 hour period.
Filtration consists simply of a small overflow which drains into a sump.
The sump contains a few small compartments for prefiltration and one for calcareous gravel in which denitrification is believed to occur. These skimmers were designed and built by hobbyists in Berlin and have been used for many years. Water chemistry is of utmost importance in both types of systems. Somewhat surprising perhaps, is the redox which varies between 180 and 195 mV as measured with a silver calomel probe. However, it is very difficult to compare redox values from one tank to the next due to innumerable variables such as probe type and pH, so any comparisons between aquariums are almost useless.