Giant danios are 4" or so torpedo shaped speed machines...they are lightning quick...they will give your devil something to chase after.
I've never seen any Biospira where I live, but I think you're looking at probably $40 for enough to do a 55gal tank. It has to be kept refrigerated or frozen (can't remember which) so it is pretty pricey, but supposedly it works great.
scott should be able to direct you to any stores that carry it in GA.