Calcium Up
You use SpaCare Calcium Up if you want to increase the calcium hardness of the bath water due to "soft water", therefore reducing the risk of corrosion of the metal parts of the bath.
Instructions for use SpaCare Calcium Up:

First, measure the calcium hardness with a dedicated meter or test strips. Then adjust the calcium hardness of the bath water to 100-200 mg/l. If you need to increase the hardness more, for example by 20 mg/l in 1,000 l of water, add 30 g = 2 x 15 ml of Calcium Up.
First dissolve Calcium Up in a clean plastic bucket and then spread the solution in the water with the water circulation running. Set the water massage to the lowest speed and then wait 15 minutes and check the calcium hardness again. If it remains low, add more Calcium Up and adjust the pH to between 7.0 and 7.4.
Recommended values
So you should be careful with the dosage and you should also check and adjust the chlorine, pH and alkali levels regularly to the recommended values:
Chlorine content 1,0-3,0 mg/l;
pH 7,0-7,4;
Alkalinity 80-120 mg/l.
Calcium hardness 100-200 mg/l
Maintenance
It is important to change the bathing water regularly and to clean the spa at the same time. This is to prevent bad and unhealthy bathing water. You should preferably use SpaCare Biofilm Cleaner to clean the built-in pipe system. Do this 3-4 times a year. After cleaning, take the opportunity to change the filters or clean them thoroughly. As a result, you get a clean and bacteria-free bathing water.
For the daily operation of the spa, you can advantageously have double filters. This means that you can quickly switch to clean filters. When one cartridge is used in the spa, the other cartridge is placed in a cleaner where you have added SpaCare Filter Cleaner. After one to two weeks of use as a filter, the dirty cartridge is exchanged for the clean cartridge in the cleaning tube.
Maintenance procedures
So you need to maintain your hot tub and Spacare has a very good instruction manual that you can read if you click here.
It's important to have fresh bathing water, right? You can find more care tips for hot tubs if you click here.