I had not realized until recently that Calcium reactors can be applied to fresh  water aquaria as well as marine tanks.

          What is a Calcium reactor and what does it do ?

          Well let me pass on the information I have gleaned from the internet and from reading books. A calcium reactor is simply a tube filled with calcium carbonate through which the tank water is pumped by a power head or similar device.

          What a waste of time I hear you say - everyone knows Calcium carbonate ( CaCO₃ ) is insoluble. Well yes and no. CaCo₃ is only insoluble in water with a pH above 8.2. At lower pH values is becomes more and more soluble - thus we can clean bricks with acid because of the low Ph involved.  

                   To increase the solubility the reactor needs some help in the form of Carbon dioxide, which is introduced into the reactor to lower the pH and allow some CaCO₃ to be dissolved into the water.

          The more CO₂ the greater the Calcium uptake within certain threshold values.   Why would you want to achieve soluble Carbonate going in to your tank ?

          Calcium carbonate/bicarbonate interchange acts as an excellent buffer - maintaining a stable pH at the level determined by your reactor settings, it also maintains a set hardness level.

          Other than plant fertiliser there is no need to add anything to your tank, to keep it functioning smoothly, without variation in chemical parameters, and at very little expense !

Whilst comnmercial units are available ( simply Google 'calcium reactors' and you will find an astonishing range), it is relatively easy to construct a unit yourself, particularly if you already use CO₂.

          A diffusion chamber is simply a fat tube or column filled with Calcium carbonate. Shell grit would be the cheapest but coarse crushed coral would be a purer form. Ground up powder is of no use as it allows no circulation of water and simply clogs.

          Water from the tank is pumped in at the slowest possible rate to allow long contact time, and CO₂ is added with a bubble counter and  control to vary the rate .

          It will be necessary to recharge the Carbonate        column periodically.          The rate of consumption depends on various factors such as flow rate, tank population etc. but as shell grit is so cheap (Make sure to wash it well before use) this is not a serious consideration.

          There is ample info available and also check on e-Bay where units appear periodically at about $200 !  ..Daryl M.

Expression of Interest

erniehicks@bigpond.com