Adult bass can be difficult to wean onto pellets (according to aquaculture literature). I tried with one years ago and it was a slow transition from live fish to frozen fish (we used sardines) to pellets. Try to get him on dead fish before switching to pellets. It may take some "wire-feeding" to get him to take the dead ones. Just tie a loose knot with some fishing line and thread it through the fish. Use the line to make it "dance" to get him to try them.