Since this question has repeatedly been discussed on the forum, and I have found no independent, scientific, peer reviewed study of Algaecal to give you as a reference, I went on a deep dive into the research of Strontium and its bone-building mechanism.
I found two very recent, apparently independent studies of how strontium is used by the body.

The first, "The Influence of Strontium on Bone Tissue Metabolism and Its Application in Osteoporosis Treatment" ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8235140/ ) provided the following details:
"The recommended dose for treatment of osteoporosis is 2 g of strontium ranelate daily, taken as an oral suspension [40]. In clinical trials, the above dose was used for three years, and in follow-up studies, long-term results were noted after treatment lasting 5 to 10 years [41]. Strontium ranelate was, at one point, withdrawn from treatment due to reports of serious side effects. Information has emerged about the growth of cardiovascular risk and non-fatal myocardial infarctions. Recently, the EMA (European Medicines Agency) has issued an overview of how strontium ranelate can be used with many restrictions on its use..."

Later in the article they add: "Orally administered strontium ranelate does not significantly affect bone formation in vivo because it does not reach a sufficient concentration near this tissue, assuming a standard drug supply and a normal calcium-rich diet."

The conclusion by these scientists: "The mechanism of action of strontium is still not fully understood, which is a significant problem in modern science. However, the research that has been conducted to date has brought us closer to understanding the mechanism by which strontium ions work in the bone formation process. It seems that administering Sr locally can be very effective, with fewer side effects than systemic administration, and it can significantly improve the osseointegration of bone implants."
Later in the article they add: "Orally administered strontium ranelate does not significantly affect bone formation in vivo because it does not reach a sufficient concentration near this tissue, assuming a standard drug supply and a normal calcium-rich diet."

The takeaway - high doses of strontium, 2 grams per day in oral suspension, provided good benefits, but not without significant risks. Research continues...

A new article : https://www.sciencedirect.com/science/article/pii/S0167732224000151#s00600 - is a PRELIMINARY study of how to influence the uptake of strontium at the cellular level in humans

So, what about AlgaeCal & it's companion Strontium Boost? The basic AlgaeCal supplement contains Calcium from algae, magnesium, vitamin D3 and a trace of strontium along with a number of other trace minerals. (https://www.algaecal.com/products/algaecal-basic/) AlgaeCal Strontium Boost contains 680 mg of strontium in capsule form, to be taken once a day. That is one-third the amount in the study referenced above, and not a liquid suspension.

The bottom line -
There is developing evidence that the form of calcium in red algae (algas calcareas)and other forms are more "bio-available" than calcium carbonate and calcium citrate.
Strontium still offers big questions because consuming large amounts can have side effects.
Only you can decide whether the price tag on the AlgaeCal products are worthwhile for you - I think there company offers a money-back guarantee with certain limitations. Or whether you can find other less expensive algae-based supplements that have been tested for purity.

Sue