With a bypass from the aquarium main pump or with a small extra pump the feed water arrives the system at the flow meter. The reactor pump circulates the water from CO2 tube to calcite tube.
At the bottom of the CO2 tube (right) carbon dioxid reaches the system - the rising bubbles are clearly visibl (bubble counter). In the CO2 tube the small bubbles form a big bubble, so the circulating water trickles down the trickling filter material. This maximum contact area enriches a lot carbonic acid. This acid water (low pH) dissolves the lime material in the calcite tube and produces soluble chalk (calcium ions and carbonate hardness / alkalinity) for corals and other lime-dependent animals.
The out-coming water from the circulation loop (CO2 tube - calcite tube) enters the neutralization tube (grey tube in the middle). With air the too much carbon dioxid is stripped. Afterwards in the sediment tube (top) the mixture of water and gas is devided into water that runs back to the aquarium, and air that goes out at the overflow. Sediments settle down in this tube, too.
After each production time (with timer operation) the system is de-aerated to prevent declining of the efficiency.