ok even tho i think my first answer was good, here's another one. IMO 1 pleco is too many as they make more of a mess than they can clean so 2 would add alot of garbage to your tank. As for the dantoid i think you have a good amount at 6. Idk how big dantoids get cuz i never kept them but but i would say add something different to you tank. Most ppl have a centerpiece fish that gets the most looks then you fill the holes with bottom feeders and some schooling fish. So i would go in the that direction or keep the dantoids as your centerpiece and leave the tank as is. Hope this helps