Use a standard food safe container (such as one made by Anchor Hocking or Rubbermaid) which I purchased at Kmart for $5.99, a Medical Valu-pak gravity feeding set (made by Medline *part number DYND70510) – here is the phone number off of the package if you can’t find this product locally *847-949-3150*) which I purchased at a Walgreens medical supply store for $3.89, two wire ties and a two inch length of rigid airline tubing.
Cut the feed bag off of the drip tube. Then insert the rigid airline tube into the medical dripper and use wire ties or a small hose clamp to make a good seal between the two. Then drill a small hole (smaller that the size of the rigid airline tubing) about one inch from the bottom of the container and insert the rigid airline tubing into the hole. The rigid tubing is inserted about half and inch into the container. I made the hole small enough so that I did not have to use any sealant around the hole but it would be a good idea to seal it (with reef safe sealant) so that it does not leak. Cut the drip tube to the length that you need and fill the container with water to test for leaks.
Remember this unit is gravity fed so it needs to be placed above the tank or sump where you are going to drip the kalk into.
This setup works well for me and the thumb wheel allows me to adjust the flow from less than a drop per second to full open. Be sure to keep the doser clean because the kalk builds up inside the rigid airline tubing after a while. I clean my doser every few days with hot water and have not had any problems. You can use any size container but make sure that the plastic is rigid enough to allow you to insert the rigid airline tubing. Do not push too hard on the container because they can crack.