The fact that they ihabit freshwater in one river in thailand (which is also very alkaline)
Alkaline? Nope.
silver datnoids in the aquarium usually come from the easter coast of india where they are caught in brackish water.
So we are told. I have only heard of AT coming from Mae Klong and surrounding areas in Thailand. They may come from further west too, where there are many waterways that are equally freshwater.
The speciments found in vietnam are also found in brackish water (formerly known as Datnioides quadrifasciatus).
No. NTT come from the Mekong and surrounding area between Thailand and Loas. They can also be found into Cambodia. But they are not found any where near the Mekong delta in Vietnam.
NTT - Quadrifasciatus and AT - Polota are not the same, apart from both being Datnoids. Not
formerly known.
AT from the west of Thailand, ST (when it existed) from the central regions, and NTT from the east. All waterways that I know and often travel on. All freshwater.
Though I do not live there, I have also traveled extensively in Indonesia, especially Sumatra, and am well aware of the waterways there where IT and RTG are found. Freshwater. Sumatra does have a large peninsular - Riau - which is salt graduating through various degrees of brackish. But that is not where IT come from.
I have not been to New Guinea, so I cannot say definitively about NGT. However, I highly doubt they are brackish.