The main difference in kalk reactors is the manner by which the kalk power is stirred. There are three primary solutions.
1) Magnetic stirring bar
These use a rotating magnet at the base of the cylinder that drives a magnetic stirring bar.
Pro's:
* The least number of possible points for leaks (fewer holes)
* No pump to clean or maintain
Con's:
* The magnetic stir systems often have difficulty driving the stir-magnet through the sludge of undissolved kalk. Myreef Systems has come up with an ingenious solution by raising the stir platform so the stir-magnet only stirs water rather than mechanically stirring the kalk. Unfortunately, in my experience the kalk can get "paste-y" and strong water movement or mechanical stirring is needed to be able to load a large supply of kalk and to stir it adequately to dissolve most of it.
Link to MyReef Systems
2) Pump agitation
Use a pump in the lower portion of the reactor to either "swirl" or "blast" the kalk at the bottom into suspension to saturate the water in the reactor.
Pro's:
* Can usually handle a large load of kalk and provide enough agitation to reach the lower levels
* Reasonably priced
Con's"
* Additional reactor penetrations, plumbing, and pump seals result in a higher potential of a leak (Most people never have one)
* Pump maintenance to clean calcium deposits or to replace parts due to accelerated wear on impellers due to circulating undissolved kalk particles (I haven't cleaned my pump in about a year and a half, but it is making noises so I ought to do it soon)
This is the method used by most reactors on the market including Geo
Precision Marine
Geo Kalk Reactor
3) Other types of stirring
The Deltec is very nice.
It uses a mechanical "stir-stick" that is driven by a motor at the top which penetrates the top lid.
Pro's:
* Decent mechanical stirring
Con's:
* Needing to keep a water tight seal around a revolving stir-rod under the pressure of your feed system.
* Price
Deltec Site
There also appear to be some units that use a more passive approach relying on the high solubility of calcium hydroxide (or calcium oxide) to reasonably saturate the water flowing through.
If you have a place to put a large container I like Randy Holmes-Farely's solution of just mixing up a large batch and pumping the mixed solution (a batch rather than in-line process). He has found that it remains highly-saturated for a reasonable period of time. Very little muss & fuss and very little to go wrong.
My 2-cents: The key considerations are -
* How little effort it takes to operate - factors include how much kalk you can load in at one time, how much effort it takes to load more kalk, maintenance of pumps or seals
* Reliability - no leaks, is not prone to locking or sludging up
Have fun,
Paul
