not all archer fish are brackish i beleive the ratio is 4 to 3 in favour of freshwater! i myself have a trio of freshwater ones and in no way shape or form in 10 gallons enough for any archer fish sorryTen gallons isn't enough for even one (I think. Depends on species).
Also, it may be worth asking a Mod to move this to the Brackish forum, where Neale Monks is a resident expert (amongst others). He should be able to give you some top quality tips on keeping Archers.
not all archer fish are brackish i beleive the ratio is 4 to 3 in favour of freshwater!