The only thing is, there may be parasites such as juvie Lernea in a planktonic stage in the water, or bacteria your fish have no immunity to, and only one could eventually wreck havoc on the residents of your tank.
You may want to thoroughly examine and wild residents of the stream.
I added some wild tetras to my tank that I didn´t notice were infected with Lernaea, and they inected everything in the tank.
I normally QT new fish for at least 3 months.
but I got impatient about 6 weeks ago, and because I didn´t see any abvious systems, cut QT short to 6 weeks.
Big mistake, within about a week, what must had been invisble larval Lernaea, started showing up yesterday on Cyprinids as adult parasites..
And today 2 floating corpses.
Even though I´m starting a double dose of Prazi today, my expectaion is the have half the fish in the tank will bite the dustin the next week.
The other potential prob could be chemical fertilizer run off if the stream’s catchment includes farm land. This could be mitigated by circulating the water through a charcoal filter for a few hours prior to putting it into your tank
Thanks for the replies, not worth the risk. I thought about the parasites but I know we have native fish in the streams here so I thought it would work. I definitely didn't consider the fertilizer or any other chemicals that could leech into the water further upstream