Brackish water, I have been hearing about them... I have heard that they need I believe aquarium salt fresh water or salt. Not sure, but they can stay in pure salt water when they are older, so then I am guessing that they can withstand the salinity levels in salt water when they are older.
Archer fishes could go with Brackish Puffers.
I was thinking that if you don't have much success you can switch to South American Puffers. They are pure freshwater, and die in salt water
So the puffers are just like the brackish ones, but they just the same like the Brackish ones.