AlgaeCal is a form of calcium carbonate, promoted by its producer as superior because it comes from seaweed and thus is more absorbable, and contains trace minerals. AlgaeCal also includes Strontium in some of its formulas, which is controversial in the treatment of osteoporosis.

There have been no published independent studies yet that compare AlgaeCal, CitraCal, and other calcium supplements in matched populations over a period of years.

I use a generic Calcium Citrate supplement from a reliable source with magnesium, zinc & D3 as was recommended by my primary over 30 years ago. At age 72, with familial risk, my DEXA scans have remained stable for over 10 years.

I think you should talk to your provider if you are confused, but continue to take an affordable Calcium supplement as well as maintaining a healthy diet, and doing weight-bearing exercises to keep your bones as strong as possible.
Sue