New member
I have gotten a Kalk Stirrer from Avast Marine Set it up and have it working, been running about two weeks now and i am starting to see the PH drop, does that mean that the Kalk is depleted even though there looks to be lots of Kalk Median remaining? It is winter here and it is a little colder, so my evaporation is a little less, but the temps have been this way for more than the time the stirrer has been running, and i use heavy duty heaters and chiller, temp swing is only .3 to .4 of a temp swing.


New member
How much of a drop are you talking about? Are you checking it the same time of day? The likely issue is the amount of CO2 in the system and its surrounding atmosphere. With less evaporation there will be less kalk being added and less CO2 being utilized, causing the pH to drop a bit. If you're getting good gas exchange, i.e. through skimming, surface agitation, etc. the only other things you could try would be utilizing a fuge with some macro algea, ATS, CO2 scrubber or the most economical method(if practicable) would be to run an air line from your skimmer's air input to an outside air source.


Premium Member
One way to tell would be to test the conductivity or pH level of the reactor water. It's possible that the media that's left has been converted into calcium carbonate, and thus is effectively fine sand. It's also likely that the carbon dioxide level is the issue, as has been suggested.


ReefKeeping Mag staff
Premium Member
It could be depleted since CO2 from the air may enter the water in an unsealed stirred reactor which would result in precipitation of the calcium hydroxide as calcium carbonate. Lower evaporation rates will also throw off the constancy of the dose. Higher room air CO2 may also be part of th pH drop.