Although water changes will help keep Ca up if demand is low, it won't help that much if they are really at 120. A 20% water change will dilute the Ca in the salt mix by 80%, and it will take the rest of your life to bring it up, even with twice weekly water changes.
First, suspect your test kit. 120 is so low I'm suspicious. Have your LFS test it, or better, buy a good kit by salifert or SeaChem. Aquarium Systems is allright as well. I don't trust much from Hagen or Red Sea.
Second, if your Ca is really that low, I agree with Corrie that there is something wrong in the tank.
One thing you noticed is that your alkalinity is too high, which will prevent your Ca from increasing beyond a certain point. The two part additive you're using has one part that adds Ca, one for alkalinity. Add only the Ca component for the moment. It's the one that doesn't make the water cloudy when you add it.
It would also help to know more about the tank. Size, livestock, how long it has been set up.
Finally, don't try to change things to fast. Dose, wait a day or so, measure, repeat. The cliche is that nothing good ever happens fast in a reef tank.
First, suspect your test kit. 120 is so low I'm suspicious. Have your LFS test it, or better, buy a good kit by salifert or SeaChem. Aquarium Systems is allright as well. I don't trust much from Hagen or Red Sea.
Second, if your Ca is really that low, I agree with Corrie that there is something wrong in the tank.
One thing you noticed is that your alkalinity is too high, which will prevent your Ca from increasing beyond a certain point. The two part additive you're using has one part that adds Ca, one for alkalinity. Add only the Ca component for the moment. It's the one that doesn't make the water cloudy when you add it.
It would also help to know more about the tank. Size, livestock, how long it has been set up.
Finally, don't try to change things to fast. Dose, wait a day or so, measure, repeat. The cliche is that nothing good ever happens fast in a reef tank.
