I was just reading a couple magazines, as well as some books, which covered the area of river aquatic life. I haven't seriously been into the aquarium hobby for a very long time, but I've yet to see a tank try to replicate a river system. I was curious as to why? Is the current too hard to reproduce, are the inhabitants to hard to find, or what? I imagine a couple of powerheads in a longer tank (55 long, maybe?) could come fairly close (as close as possible in aquaria, anyways) to reproducing a natural river habitat. If anyone has any input, or resources that are around, please let me know. I'm pretty interested.