I believe biopellet does not effect your alk. Did you just start using biopellets? also taking off biopellets cold turkey can cause more harm then good. I would keep the biopellets and run smaller amount gfo to fine tune your p04. Be careful when running gfo because overloading it can strip your tank so i recommend you looking into this product .
http://www.madjellycorals.com/#!prod...sphate-remover