IME I would not put a pair of mono, scat, or archer in a tank together!!!! These IMO are all schooling fish and when there are just 2 they tend to take their aggression out on each other. I would at least do groups of three with these fish that way the aggression can be spread out a little! I would also suggest doing scats and monos they are amazing fish, but be warned they will both need full salt water as they mature.
The main thing is that there is no "BW Standards" All brackish fish have different needs and it is important to understand this. F8 Puffers, BBG, And Archers do best around 1.005 - 1.008 While other BW fish such as Monos, scats, Columbians, MORAY, like 1.010-1.018 increasing to full marine as they become adults. Do some research and pick fish that can live in the same water parameters, because if you don't, you will learn the hard way like I DID, and need to re-home fish as the salinity increses.
