I suspect these to be Parioglossus raoi but am more than happy to be corrected.
One of several "freshwater" Dartfishes I have been maintaining for awhile now. Imported as Parioglossus winterbottomi, however these are definitely not that species as they originate from Indonesia (P. winterbottomi is endemic to India). These were collected far inland away from an estuary or mangrove.
They prove hardy and have even shown breeding behaviour, however it is likely that they will require saltwater to spawn.