BraveheartCalif;2882712; said:"pectoral fins of the black goliath are much thinner then those of the main river mbenga"
Adding black water isnt going to make the pectoral fins thinner---
True, but the black river mbenga is a small side shoot, of the main river, read that as the water flow is more powerful in the Congo river, one of the most powerful rivers in the world. That difference in the power of the rivers would affect the thickness of the pectoral fins, and a possible difference in chemistry/dissolved solids/tannins etc.. may affect color.
Two separate characteristics, two separate variables.

