According to Wikipedia, The Great Fish River was given the name 'Great' to distinguish it from a river that was already called the Fish River in Namibia.

The Sabine River marks the borders of these two great territories. This river is a great placefor recreation. You can boat, fish, and, well, sightsee!

Yes, it is bad to put tropical fish in with river fish. The river fish can make the tropical fish sick.

Yes, you can fish in the Colorado River.

Rhine River fish.