Greetings, I'm looking for info on Argentus Mono fish. I know they are Brackish fish, and as they get older they should be moved to a saltwater environment. I know they require large tanks, however I've also heard. Some Monos' are breed for fresh water aquariums. How true is that fact and how long do they live in a fresh water environment? I've seen a few at a local pet store they look nice. A friend of mine brought 3, they seemed to change color to a grey/black when they were introduced to the new tank. Hours later 2 changed color, back to silver and one was still grey black. What might of caused this?