I just finished about two weeks ago installing my calcium reactor.
They way they work is by bubbling CO2 through the reaction chamber and mixing with water you create carbonic acid driving pH down below 6.9 This dissolved the substate (slowly) releasin perfect trace elements (except iodine). This is fantastic for all stonies, heavy fish loads, Clams, big tanks (where dosing can be expensive).
Then by dripping the effulant back into my sump (about 6" drop) the CO2 De-gasses from and your pH of the effluant pops instantly back up to around 8.3. Depending on your flow rate you can tweek the feed ammount of Ca, KH, and trace elements.
The only thing I found is that there was not an adiquate ammount of Magnesium coming in from the reactor so I still dose with a magnesium suppliment weekly, and Iodine.
Im running a Coralife reactor with a reefkeeper controler. The controler keeps the pH between 6.7 and 6.4. This limits the wastage of CO2 (using a 20lb beverage grade CO2).
Prior to the application of the reactor my clam tank would drop my Calcium from 480 to 230-255ppm in one night. The KH would go from 220-120 in about 9 hours. I was dosing 15ml of purple up twice a day (that's a 300 gallon tank dose) My clam tank is 40 gallons.
This led to a pH swing which my acros did not like.
Now, with the reactor balanced and running my KH is holding exactly at 200ppm (i run a little high), and Calcium at 500ppm (a little high).
I will pop some pictures and post them when I get home today.
Here is a pic of the clams
If you can afford it run with a power controler on a solenoid (co2 supply) it will be well worth it in the long run.
Any questions on sources just message me.