Some of the plants I find in rivers and streams are not what you might expect.
Few really fast streams have plants, maybe moss will be about it.
1-3 mph is about the limits.
Vals, Myriophyllum, swords, Crypts, Crow's foot, Waterworts, most floating plants, Crinums, Ferns, Anubias, these all come from rivers.
They will grow in our tanks with or without strong current, but I think if you sit down and really consider the aquarium, as eluded to by others here, high current is good for fish.
Why?
The plant beds really reduce flow rates.
So fish have a place to get away if they wish, but in the higher flows areas, they can get a decent work out and this acts like a much larger tank where they can really swim around in.
They get more exercise and eat much better, grow better, are more healthy.
Plants tend to stay cleaner, less settles on them, more compact growth forms.
I have Rotala wallichii right in very high flow, does great, grows about 1" per day under high light, I have to prune it aggressively weekly.
Regards,
Tom Barr
Regards,
Tom Barr