I currently have a 45 gallon tank in which I have 3 black tetras, 2 white tetras, 1 red tailed shark, 1 koi angelfish, and 1 siamese flying fox. I would like to add either a bolivian ram or German blue ram...my question is which would be best? And should I get 1 or do I need a pair? Water parameters ammo 0, nitrites 0, nitrates 5.0 ppm, ph 7.6...any other suggestions on what to add? I mainly want the rams because of their color. I kind of want a centerpiece to add to my tank. Thankyou