Running GFO and Bio Pellets?

[Lampshade]

I notice that my PO4 goes up after a cheato harvest. I imagine it's because the cheato regrowing it taking up nitrates, and so my biopellets are no longer balanced. But i've not seen a need for GFO while running pellets, everything seems to stay nice and balanced, with even some extra nitrates that i'll bomb with vodka every once in awhile.