It's dangerous if you don't use it properly. Research carefully before using if you decide to. It does work, I'll give it that. Really not a long-term solution, though. Best to look into the cause of your phosphate problems.
the only reviews I can find say it is not for beginners AND you need to test your PO4 faithfully while using the product...so I would make sure you have a good test kit available.
have you considered another product like GFO or ROWA Phos ?