Kalkwasser reactors (often referred to as Nilsen reactors) are designed to mix incoming top off water with kalk powder (Calcium hydroxide, Ca(OH)₂) to provide a makeup water source supersaturated with calcium/alkalinity. Freshly mixed kalkwasser has a pH of about 12. Traditional mixing methods such as buckets or other containers for dripping expose mixed kalkwasser to atmospheric CO₂ which causes precipitation of calcium carbonate and renders the kalkwasser much less effective. Utilizing a sealed Kalkwasser reactor from Aquatic Systems Design prevents this from happening and makes your kalk much more effective.