Here is a study that talks about the efficacy of AlgaeCal (AC) from the NIH, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3053489/. Of note, the study did conclude that calcium supplements in combination with increased activity did have positive results for many. It also mentions that adding any supplements should involve your provider as well. @healer74's experience with AlgaeCal is similar to what a study from the NIH confirmed through research results in 2010 when they determined mild to no side-effects, https://www.ncbi.nlm.nih.gov/pubmed/20528255.
@grace1215, how bad is your osteoarthritis of the hip? I have experience with end-stage arthritis in knees and ankles and know that when arthritis reaches that point, it can cause pain and mobility issues.