Andy Sager
Aquarium Advice Addict
You can tell people not to mix cichlids for all sorts of environmentally and zoologically sound reasons, but the fact is, despite how hard we try, we are keeping aquariums, not natural habitat. The parameters and comfort zones will vary, regardless of targeted conditions and skills applied in achieving them. It can be done, and done well.
Will do.
Granted, we do keep a number of different species of fishes together in aquariums that would not be found together in nature HOWEVER, that does not mean that all fish can be kept together. An Oscar, for example, will still eat a Guppy whether it's a wild one or a tank/farm raised variety. A BA tetra will still chew off the fins of a frilly finned fish and a fish that needs a high mineral content water will not do as well in a low mineral water just as a low mineral content water fish will not do well in high mineral water. SOMEBODY will be suffering and not living their best potential life. So there is a very small, if any, window of comfort zone for contrasting fishes like these. Considering that the OP is talking about fish that very well may be wild, care should given as if they are working with these wild fish.
Just my opinion.