Restricting Kalk to dark hours


New member
I'm currently running Kalk in my ATO in conjunction with a calcium reactor to keep my pH from falling too low. Currently based on consumption, I'm using 1 teaspoon of kalk per gallon of water only, but eventually will increase it to 2 teaspoons of kalk per gallon (I'm not going to bother fully saturating it or adding vinegar to increase saturation etc. It will just max out at 2 teaspoons of kalk per gallon, and the calcium reactor will take care of the rest).

My tank has about 180 gallons total system volume and it consumes approximately 3-5 gallons of ATO water every 2 days. Currently, I run the ATO to just top up whenever it detects the water level is low. However, in order to maximize the pH buffering effect, I'm thinking of switching the ATO off during the hours of light when the pH is already naturally higher, and switching it on only during the dark hours when the pH drops - in this way, I hope to be able to smooth out the pH fluctuations.

My question is whether this more "concentrated" shots of calcium/kH/pH dosing via kalk where the ATO is limited to 8 hours a day instead of over a 24 hour period would be harmful to my tank. This is a full SPS tank, so the corals are more sensitive than softies or LPS.



Grizzled & Cynical
I use dual ATO pumps, one through my kalk reactor the other directly to the sump. When pH is below 8.2 I have my apex use the first one, otherwise the second one. Less frequent use of the limewater seems to have no negative affect.


New member
That's brilliant! One day when I free up enough space in the sump for a kalk reactor I'll definitely be doing that too. For now, I'm stuck with 1 pump and kalk in the reservoir