<a href=showthread.php?s=&postid=13660272#post13660272 target=_blank>Originally posted</a> by Nuuze
What about dual chamber calcium reactors?
It takes some time for the media to get dissolved and stabilize the ratio of carbonic acid to bicarbonate inside the reactor.
As the CO2 dissolves in the water it forms carbonic acid only. As the carbonic acid dissolves the media it adds bicarbonate to the point both are in balance.
When the first chamber is smaller, a second chamber is added to increase the time the solution is in contact with media for this balance to be achieved thus increasing the proportion of bicarbonate which in turn increases the PH of the solution.
See, the alkalinity takes three different forms depending on the PH, carbonic acid, bicarbonate and carbonate. At high PH (close to 9) it is mostly in the form of carbonate. At lower PH (*.2 to 8.4 the three forms exist although the bicarbonate is the form most prevalent. As PH drops the most more of the carbonic acid form exists.
At a PH of about 6.3 the combination is about 50% carbonic acid and 50% bicarbonate with almost no carbonate. It takes time for this balance to be achieved so if you pass the solution trough the reactor too fast, it will contain more bicarbonate than it should thus increasing the PH lowering effect.
In simple words the end result of adding a second chamber is to increase the PH of the reactor output, improve the consumption of CO2/carbonic acid by allowing it to convert more thoroughly and increase the capacity of the reactor. This also allow for shorter reactors that can better fit inside a stand although it trades vertical space for horizontal space.
There are other means to help increase the time the media is in contact with the solution other than increasing the first chamber size or adding a second chamber. The simpler of which is to increase the flow capacity of the recirculation pump.
Every time the solution is circulated trough the media it is equivalent to one time the height of the reactor so if the solution turns inside the chamber 10 times before it is released to the aquarium that will be equivalent to a chamber that is 10 times higher. My say doubling the flow capacity of the pump you double the number of turns thus doubling the equivalent height of the chamber and as a result doubling the time the solution is in contact with the media. This is why, as the media dissolves the capacity of the reactor decreases, less height in the media column as well as more mud which partially clogs the flow reducing the number of turns. Although the media does not need to be replaced, this is why I always recommend to top off media when it reaches 3/4 of it's original height and once in a while (every 4 to 6 months) I recommend taking all the media out and rinse it as well as rinsing the reactor and any foam that might be used to support the media.
Hope this help although it might have been more detail than what you were looking for.