[Daeorn]

African Butterfly fish btw, are not brackish? Hm.
I've read that they can be kept in brackish, and even in some articles I've read - that they are sometimes found in brackish waters. (not disputing you, I would be dimes on the dollar you know more about it than I do)

The needle nose I'm refering to is the silver needlenose, what I have read is a freshwater/brackish water fish that grows to be around 8" tops in captivity. (Again, you are definately more the expert than I. Just going by what articles I've read)

The needlenose and eel I can live without, the dragon gobies I already have, and would like to keep.

Would it be possible to have the tank at a low salinity, with 3 dragon gobies, 2 archers and the butterfly?

If it helps, the tank is a 75 long, 4 feet wide, none of the fish, including the gobies at more than 5". I know the gobies can reach a foot, or so - over a period of years.

The archers get what, almost 6" when adults? Not much more for the butterfly.

Just trying to arrange a decent low-end brackish with some interesting fish.
The salinity would be around 1.0002-.0004 I think at most.

Trying also to arrange my tank by - bottom dwellers, middle, and top dwelling fish - while going off the 1 gal of water for every 1" of fish.

Any ideas? I don't out right want to harm any fish - of course. I want to know if there is a comfortable balance between them.

It's a pretty decent size tank, good cover, and various "caves".