Just curious, I know sk8r said he tossed his but if its as simple as dumping kalk into your topoff water, why use a reactor?
I can give you a quick overview of the kalk reactor....
Kalk reactors give you separation between the kalkwater mix and your topoff pump. I run a PM Kalk reactor on my 125 - I have a water bucket that is kept filled with ro/di - and then the reactor filled with ~ 1/2 a large can of the kalk power at a time. The topoff pump feeds a line into the reactor (stop valve to prevent backwash) then the reactor feeds the tank. The reactor has a pump to stir the kalk at specified intervals (I have a controller managing this).
Benefits of a kalk reactor -
Kalk is sealed. PH of the slurry is high - and can be somewhat messy. The PM system is sealed so the mix is not accidentally exposed by the stray pet or child poking around. This also helps to extend the life of your topoff pulp. The high PH of the kalk mix can really bring down a pumps lifespan. I was using aqualifter pumps - and for a while had a bad stop valve so some of the kalkwater was back-filling into my topoff bucket (water levels caused a siphon to the kalk reactor at times). Pump gave out after like 8 months (I was LAZY in fixing the issue). With a good stop valve- more than a year for the pump.
Stirring - since you can dump a lot more of the kalk mix into a reactor - you also can have an element to mix up the batch to limit clumping. The PM has a max-jet pump that is directed at the bottom of the chamber. I usually run this about 5 minutes a day. Of course - this is made more necessary by the reactor itself - adding directly to topoff tank is usually done in smaller batches of kalk mix so you do not have to worry about clumping as much.
Plumbing - the PM reactor water inlet is at the bottom of the reactor - taking water for the display tank from the top. So the water flows upward You also are consistently pumping the fully saturated water into the tank, leaving teh slurry at the bottom of teh reactor. A setup like sk8tr has - you have to keep the pump elevated in the topoff tank so you do not pump particulate into your tank. I do not have a large topoff bucket (like 5 gal) - so if I tried the direct method, I would be adding topoff water every day (maybe more).
So - does anyone really need a reactor? Probably not for smaller tanks, but for larger ones (I have a 125g) - they help with making the process simpler with less time to maintain (you can add a LOT of the kalk into the reactor at once).
They also require a little more control than just adding to topoff water. If you use a stirrer - you need to make sure the topoff pump is not active at the same time - and even longer as you want some settling before you run the pump. The PM guards somewhat against this - as the "white" cloud during stirring is at the bottom half of the reactor chamber (the water to the tank feeds from the top) - but this is still a concern as you will see in a moment -
Can there be problems - YOU BET!
The ability to dump a couple months worth of kalk powder into a reactor does not mean that you can stop paying attention. You still need to refill these things. I have had great success with my reactor - but yet having this fueled my own laziness! Twice I have had mini "coral" crashes caused by not recognizing when I needed to fill the chamber (the reactor is not in plain sight). Having good growth told me things were "ok" - so I was not regular testing for CA and ALK. While corals can grow and survive with lower levels - what they really hate is RAPID swings. Once the kalk is gone - a demanding tank can really strip away the needed alk/ca and you are fighting the uphill battle to get things stable again.
The other end - you need to take care to remember that the more automated you make your system - the more issues you may cause yourself! So - established earlier that I can be lazy with some maintenance items. Sometime I will let my topoff bucket go low. Once - the sump was probably a gallon low so (topoff bucket dry), so I refill it.
I did not notice that the kalk stirrer had just finished running. So - even though the reactor draws water from the top - I added in a lot of the particulate in the water column as I was pumping a lot more water back into the system than is normal. Later that night - foxface in distress and I saw that the tank PH had JUMPED to 10 earlier after the topoff water was added. Was back at 9 at the time I noticed the fish which was almost lights out time. I was patient as the PH drops at night - did not want to over-correct and crash the PH. Next day - fox was fine and PH back to normal. BUT - will never let that mistake happen again (letting the topoff cover too much evap at once).
So for kalk - adding to topoff water or using a reactor are both great ways to help maintain ALK and CA. Simplest with more day to day maintenance is adding to the topoff water bucket.
Less maintenance intensive but more expensive to set up is a reactor. Do NOT think it is foolproof as this fool can attest - but I would think that this is the preferred method for larger tanks.
Later