you have too have an archer fish 8) , salt water straight from ocean , should be okay belong as you get it from a clean area , then mix with freshwater until you get required salanity Monos and scats get fairly large so do archers eventually
there are ,monos , scats , puffers ,archers , mollies also do very well in brackish conditions , chromoids (sp) ? , bumble bee gobies off the top of my head , you should give living art a p.m he has an awesome brackish tank , with some nice fish 8)