Thank you very much I didnt knew exist product to rise phosphates, I will search to buy it.
If you do find that particular brand, I like the instructions on it – they seem conservative and very comprehensive.
Do it just like they say, IMO. They say to target from .01 ppm to .02 ppm – in your case I'd say target .02+ ppm. (I don't think even up to .05 ppm should hurt anything.)
Make sure to keep a regular eye on your progress with both NO3 and PO4!