I second white clouds as a great option for an unheated tank with a lot of movement.
Small non-annual killies would do well if the tank is lidded.
Small tetras or rasboras if the temp doesn't drop too much (or you can get a small heater). A 9 gallon would let you do 2 small schools if you stick to nano-size ones like ember tetras or kuboti rasboras.
Guppies are pretty tolerant of the temps, and would be fine in a moderate current if you stick to more wild-shaped ones and don't get delta-tails.
You might also look at nano fish that are USA natives. Even the ones from hot places like Florida get a seasonal temperature drop, and should do fine in an unheated tank in a climate-controlled home.
Also, I found that loosely tying a square of flosspad over a strong outflow, so that it doesn't restrict the output but rather disperses it around, allows me to keep fish that don't love strong currents in tanks with high-flow filters. You may want to tinker with that before deciding on stocking.