Kalkwasser Reactors REEF OCTOPUS / REEFTEK KALKWASSER REACTOR   Reef Octopus kalkwasser reactors are used for dosing kalkwasser (calcium hydroxide) in reef tanks. A kalkwwasser reactor, used in conjunction with moderate water changes, should be able to keep up with calcium and alkalinity demands in lightly stocked tanks. Kalkwasser Info Translates from the German for limewater and is a solution made by dissolving Calcium Hydroxide in water. The resultant fresh solution is alkaline with a pH of 12.4 and contains a ready supply of both Calcium ions and Carbonate ions. Both of these ions are useful to the aquarist as the Calcium ions are available to the corals and the Carbonate ions help to buffer the pH. There is an added benefit in that kalkwasser also precipitates phosphates from the water. If the evaporated water loss is replaced with kalkwasser then it will add calcium and offer the other benefits described above. Unfortunately fresh Kalkwasser is unstable and reacts with CO2 in the air rapidly diminishing in the level of free calcium. For this reason it is necessary to continually make a fresh solution and to keep it away from the atmosphere. This is where the Kalkwasser stirrer comes in to play as it continuously makes up fresh saturated solution as it is used up. Note that great care must be taken when administering Kalk due to the great affect that it has on the ph of the aquarium.