Bristlenose pleco is always good. I have one in my 29 Gallon and it does not bother anything. I've heard Normal Pleco's can rip apart a planted aquarium when they get very old, and could possible suck the slime coats off Discus.
46Gallon Natural Planted Tank. 8 Harlequin Rasboras, 5 Amano shrimp, 2 German blue Rams, 1 Dwarf Gourami, 5 Platys, 1 Albino Bristlenose