2nd Stage for Calcium Reactor
Picture from November 2000

This is a second stage chamber that I added to my K2R Calcium Reactor. This is a prototype design created by Tim Marks (fellow reef keeper who went on to found the EcoTech Marine company). The media chamber is made of 4 inch clear PVC tube and 12 inches tall (he has other prototypes 18 inches tall).

Why use a second stage? The effluent that comes out of most reactors tends to be around pH 6.5 to 6.8. That effluent water still contains a lot of CO2. The second stage provides a more area for media in which the effluent must pass through before returning to the system. This helps to dissolve a little more calcium and give the reactor a bit of a boost. Or, if your not looking for a boost you can use it to lower your existing CO2 usage and this is the main reason I use it.

Caribsea A.R.M. Reactor Media is ideal for a second stage unit. It dissolves at a much higher pH value. CaribSea claims it will dissolve at pH 7.5.

Top View of 2nd Stage for Calcium Reactor
Picture from November 2000

Effluent from the primary K2R reactor enters the second stage at the bottom via the ¼ inch compression fitting (see below). The effluent flows up the media chamber and exists out the top of the 2nd Stage and returns to my sump.

I would suggest you tune your primary reactor first. Measure your effluent alkalinity levels from the reactor. Then add a second stage and use a media like CaribSea's A.R.M., then re-tune the reactor. You should be able to lower your CO2 usage and get the same effluent alkalinity.

Bottom of 2nd Stage for Calcium Reactor
Picture from November 2000

This is where the effluent from the primary K2R reactor enters the second stage via the ¼ inch compression fitting and works it way upwards.