Biopellets is used mainly to control the nitrate level in the tank.
Goodbye PO4 like all other liquid PO4 removers are used to reduce the PO4 levels quickly. They do not maintain the PO4 levels over the long term in any tank. For maintenance of PO4, you will to use PO4 media like Rowa Phos, Aqua Media Phos FE etc.