Yeah that's what I was thinking. Well some type of tetra. I like the blackfin tetras also. Definitely not trying to stuff anything in there that will cramp him up.Nice fish! As for stocking ideas, you could try some larger bodied tetras like colombians. Should be quicker and harder to decapitate than the guppies!
Other than that your 75 will be full once your terror is an adult, sounds like he is living up to his name too! Will be a nice silver GT