You'll need to add calcium yourself.

Yes, if your fill water is naturally soft, you have to raise calcium hardness manually. Soft water is aggressive—it wants to dissolve minerals, which means it will eat at your pool plaster, grout, or even your heater if left unchecked.

Get a test kit or strip. Target 200–400 ppm calcium hardness. If you’re way below that (common with soft tap water), pick up a bucket of calcium chloride (often sold as “hardness increaser” at pool stores). Follow the label dosage: usually about 1 pound per 10,000 gallons raises hardness by 10 ppm. Dissolve it in a bucket of pool water first, then pour it near a return jet with the pump running.

Don’t bother with expensive “chelated calcium” or fancy blends—straight calcium chloride works fine. And no, you don’t need to balance calcium hardness weekly. Check it a couple times a season, or after a heavy rain or refill.

You just can’t ignore it with soft water. Future plaster will thank you.