the problem with me using CO2 is I don't know where to put the cylinder of CO2. I now know how the Ca reactor works. Would dosing kalk work, the tank is only 75 but I am looking at enlarging the system by adding another tank. So there will be about 100 gallons of water.
Thanks Eric

Kalk works as well as other Ca supplements.

Back this up a bit, what are you keeping, as in do you even need a reactor? Are you now measuring your Ca levels and how much is being depleted daily/weekly?

I am planning for the future as I will be keeping hard corals also since I sell marine merchandise I like to kow how it works. Meaning I like to make one for myself then use it. My system that I am thinking about has only been running two months roughly.
Thanks Eric

Does a kalk reactor do the same thing or is it the same thing/.
Thanks Super7

Different than a Ca reactor but similiar in that they both add Ca. No CO2 bottle required.

See here

A Kalk reactor is different than a Calcium Reactor. A Kalk reactor used Kalk powder which is mixed in a freshwater solution. The freshwater solution is then dripped into your sump usually during the lights out hours of the tank to raise pH or with your auto topoff system.

A Calcuim reactor uses basically old coral skeletons and dissolves them in a mixture of CO2 and salt water from your aquarium. The CO2 lowers pH to about 6.5-7.

Kalk seems to raise Alkalinity and maintains it quite well but not so much for Calcium levels. The solution is very basic (i.e. pH 12 or so) so care must be taken when dosing Kalk solution.

Calcium reactors raise Calcium levels and maintains them well but do not maintain Alkalinity as well as Kalk. The solution has a moderately low pH (usually 6.5-7).

As for building either, I would say a Kalk reactor is *slightly* easier to build than a Calcium reactor since it has fewer parts, but neither of them are terribly difficult to figure out and build. The inital cost of setting up a Calcium reactor is higher, but the overall maintenence of it is lower than a Kalk reactor.

How small can you get a CO2 canister
Thanks Super7

5lb is the smallest that I've seen used.

Thanks mr alberta
Super7