6
Fig. 2: Calciumreactor KR 5000
2. Theory
The equilibrium between calcium and carbonic acid in a seawater aquarium is destroyed due to the biological
activity of the animals. For the construction of their calcareous skeletons, they take calciumcarbonate out of the
water. As a result, it comes to a lack of calcium and an increase of the pH value. The Aqua Medic
Calciumreactor
KR 5000
is a module for the adjustment of the natural equilibrium between calcium and carbonic acid in the
aquarium. It is filled with Hydrocarbonate, a highly purified calciumcarbonate. Because this calciumcarbonate is
not soluble at pH values common in seawater tanks, it is necessary to blow carbonic acid into the reactor. This
results in a local drop of the pH value and simultaneously to the dissolving of calciumbicarbonate.
To avoid an overdosage, the addition of carbonic acid can be controlled by use of a pH controller or pH computer.
This method does not change the pH value of the aquarium water.
Chemical reaction:
CaCO
3
+ CO
2 +
H
2
O -----> Ca(HCO
3
)
2
Calciumcar Carbonic acid + Water ------> Calciumbicarbonate
Calciumbicarbonate is easily soluble. It can be directly taken up by animals and plants and integrated into their
skeletons. By doing this, calciumbicarbonate is changed back to calciumcarbonate. During this back reaction,
CO
2
is released which is used by Zooxanthellae for photosynthesis.
3. Working principle
The
Calciumreactor KR 5000
is supplied with water at the water inlet (1). The flow rate should be adjusted
that way that the ph-value doesn’t exceed 8.3 during the day or sinks below 8.0 at night. The pump circulates
the water internally. The CO
2
is connected at the injection port (3) at the bottom of the reactor. Through the
rotation of the impeller, the CO
2
will be completely dissolved in the water. Then, the CO
2
enriched water is
pumped below the Hydrocarbonate and finally circulated. Thereby, calciumbicarbonate is extracted from the
Hydrocarbonate. This is exactly the combination which corals need for their growth.
The outflow is located in the top of the filter. From there, the water flows into the aquarium or back to the filter
tank. The carbonic acid can be added from a pressure bottle
.
4. Set-up
This version of the
Calciumreactor
is a closed system. The reactor can be installed below the aquarium from
where the water can flow into a filter chamber or back into the aquarium.
