Yes. Mix it with freshwater and slowly drip it into the tank. If it goes in too fast, it will drive the pH too high.
In the past I have used it for all my FW topoff water, and it will help keep Ca in a good range if the demand isn't too high. I used a Kent Aquadose with a DIY sloenoid valve, and you can get more elaborate with a dosing pump or kalk reactor. Somebody I knew just used a plastic cup with a hole in the bottom to release it slowly, and it worked fine for a nano.
You can also add white vinegar to the solution to reduce the pH of the solution, keep alkalinity up, and dissolve a little more Ca. I used about 50 ml per gallon of kalkwasser. Try a search on kalk or kalkwasser on the forum here, you should find some other people's opinions and a few linked articles.