I have a tropheus I bought from petsmart that would only eat bug bite pellets and random debris/algae he finds in the aquarium but will ignore the crushed peas I throw in the water. What am I doing wrong?
That's normal. They are not vegetarian. They are limnivore or so called Aufwuchs grasers. Means they feed on algae and all the small creatures living in the algae.
I feed mine high quality flakes with minimum 10% spirulina (good substitute for algae) as staple food and in addition some pellets and some low fat low protein frozen foods like daphnia.