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The reef tank is exposed to air and the storage pumps are circulating the water throughout the filtering system causing significant amount of evaporation. You will need to replace the evaporated water regularly. “The water evaporates. Not the salt”. Do not add salt mix with the make-up water. This may result in higher salinity.
Adding make-up water provides good opportunity to replenish much-needed calcium, which gets depleted rapidly in an enclosed reef system. The best calcium additive is “KALKWASSER”, which is calcium hydroxide. It is added on regular basis by mixing it with the purified water being added to compensate for evaporation. These regular additions of calcium hydroxide also keep the pH level elevated to the desired 8.2 to 8.4 level.
Kalkwasser is a German word and literally means lime water. Kalkwasser is a trade name for calcium hydroxide.
The water you use to replace what has evaporated is called make-up water. It is extremely important to use purified tap water mixed with calcium hydroxide for the make-up water.
When to add make-up water?
Add the Kalkwasser within a day after you mix it; it gradually loses effectiveness after it is mixed. Watch the water in the sump. This is where you’ll see the change in water level. Once you have established the working water level in the sump, mark it on the side of the sump box, with a magic marker. As evaporation occurs, watch the mark. When the level goes down by 3 to 5 gallons, or get close to the top of the outlet for the pump, you need to add make-up water. Mix the water no more than one day before you add it to the tank; it starts to lose effectiveness right after it has been mixed. It will have the highest concentration of available calcium just after the sediment settles out of the solution.
On a smaller tank, 5 gallon of high-powered make-up water must be used with caution. Kalkwasser has an extremely high pH. Pay close attention to the dosing flow of water, to be certain that it is administered very slowly. For a 55 gallon tank, you should take a 48 hour period to administer 5 gallons of make-up water. Adding Kalkwasser too fast will cause pH shock, which can be fatal.
Time of day to add:
Add the Kalkwasser mix when the tank lights go out, or first thing in the morning. While the lights are off, the pH drops, reaching its lowest level the next day just before the lights come back on. Do not mix with an airstone, this will add carbon dioxide and oxygen, which will reduce the effectiveness of the calcium hydroxide and defeat its purpose.
Benefits of adding Kalkwasser:
– It adds calcium that is needed by most of the creatures in the reef.
– It encourages the growth of pink and purple coralline algae.
– It keeps the pH level elevated. By adding Kalkwasser on a regular basis and doing water changes every 2 to 3 weeks maintains the pH between 8.2 to 8.4
– The reef just seems to love Kalkwasser.
– Helps maintaining a healthy reef and desirable water chemistry.