I asked a friend in the know about fish.
Ďsentani is endangered in nature because of introduced species.
But this and all the others arenít difficult to find in the trade, because theyíre so easy to breed. Hope they have a big tank, apart from parva theyíll all grow to 12cm.
Iíd make sure itís very well oxygenated, as these are very lively fish and will not tolerate low levels. Theyíre also very greedy, so will eat just about as much as you throw in.
So feed moderately, lots of o2
and monitor nitrate etc. I think theyíll need lots of fast growth for export. Hornwort is good for rainbow tanks because it likes the water parameters.
If these fish do prefer harder water Iíd mix Your top ups with a bit of tap too.
If it makes you feel any better I think Walstad kept some if her best tanks with rainbows.