If you really want to keep both the raphael and shark in the same tank, get lots of pieces of wood, plants etc to keep on the bottom and break up line of sight. I have a rainbow shark and african featherfin catfish sharing a tank and since they have had more wood and plants added, they hardly if ever get aggressive with eachother and when they do, one is always quick to move somewhere else. I also have angelfish in the tank and so far I don't think the shark has even noticed they exist, or if it has it doesn't care enough to nip at them because they hang around the middle and top of the tank.