It seems in the winter and in summer I receive e-mails asking how to increase the pH level of the tank. If the alk is at 3 meq/L (8.4 DKH) or more it is most likely you have a co2 issue within the house. This is due to most houses being closed up due to the outside climate. It is even a bigger problem with newer house as they tend to be air tight.
If your alk is 3 meq/L (8.4 DKH) you do not have to dose more unless you want a higher alk. Remember if the problem is co2 then extra dosing does not address the problem.
Take a cup of tank water at the end of your light cycle. Test the pH. Then take that cup of water and airate it outside for 1 hour. If the pH goes up you have a co2 issue in the tank. The reason you want to take your pH test at the end of the light cycle is this will be the highest pH level that the tank can produce. As algae produces oxygen during the light hours it raises the pH.
For co2 fixes you can do one or more of the following.
Open the house to air out the co2. Although this is a quick temp fix it will get you a boost if you need to more. It will also increase the health conditions of the house for you too.
Run your skimmer line outside the house to bring in fresh air. Just remember to place a inline carbon filter to help remove contaminates from outside. Change the filter every six months. If you cannot run it outside you can use soda lime in your airline filter instead. When it turns purple change it.
Add a refugium to the tank. If you have one make it bigger.
If you dose Kalkwasser you may not want to use a two part. The chemistry works different and can clash. If you have to due to a higher calcium demand then drip the kalk a few hours after the lights go off and have it stop a few hours before the lights come on. Dose the two part in the morning as usual.