All the datnioides species *can* be kept in fw. Silver Datnioides/American Tigers do alot better in brackish conditions.
None can live in a 120 for life. They do grow incredibly slow so it will take many YEARS before any of them outgrow a tank that size.
I bought my thinbars from TFD and they are awesome. They were small but had full necklace and some intense coloration. I bought some wide-bars from Rare Fish and they are awesome too.
oi man i filmed my dats railing a turtle... i caught my dats off the coast of jamaica using 30 pound line.. but i heard you can buy them off ebay for cheap doggs..