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. Ozone is not used in this system. Activated carbon is used every three weeks for a period of a few days and is then removed. Hair algae must of course, be totally absent before any hard corals are introduced to an aquarium.