Hi Jeremy,
I guess with that size of tank, you can go with anything you like.
Just read up on compatibility between species, and try to create a peaceful as possible environment. I don’t support a tank filled with fish from different parts of the world, or even sometimes from different places from the same part.(e.g. Lake Malawi, Lake Tanganyika or lake Victoria). You could try to recreate a part of a certain habitat in your tank.
Considering the partial water changes you have to perform, which would be approx. 60 gall, I would check up on your tab waters pH, and choose fish based on that, it’s much easier to raise it from 7 to 8 than to lower it from 8 to 7.5 not to mention 6.8.
These are just a few points worth considering. I can’t give you any recommendations as I’m thinking of changing my 120gall mbuna tank into a Central or South American tank.
The only thing that keeps me from doing it, is my tab waters pH which is 8.4.
I’m trying to find a way to lower it close to neutral with as less effort as possible.
So, all I can do is wishing you good luck with the setup of whichever tank.
P.S. Keep us informed about your choice and progress.
Jimmy