Check out Wildwoods site, they have Toxotes microlepis which they are saying are freshwater. I have seen them in the store for a while and they seem to be doing OK. But as you put, you reckon they will need salt at a later stage in life, interesting, do you have pics of the freshwater varieties? Would love to keep some but don't have the room for a brackish tank.
Rich
I'll have to track down the pics, although they're vary scarce on the web. I've only seen T. blythii which has "marbled" like markings, 4-5 longitudinal broken stripes... absolutely beautiful. T. lorentzi looks like a stressed out T. jaculatrix/microlepis, chatareus... kinda dusky brown/gray/black... pretty ugly actually.
I've never seen either of them in LFSs. I wouldn't expect to see any of them either since they're not commercially traded. However, I have heard rumor that we might expect to possibly see T. blythii in LFSs some time this year, maybe... don't hold your breath.