I have a 2.5 gal
I left the filter running and tried to baffle the flow with the fake plants, but it still had enough current to make sushi not move as much as before. Half way thru today i unplugged the filter and 10 minutes later he was as active as ever before.
I did notice something though, and it might be something i have to keep track of, but the water temp hit 80-82, hotter then it had before. I think it had to do with having the light on. I unplugged the heater that i bought and left the light on and the temp stayed around 78-80 for the rest of the day. I have a fairly draft office which prior to today had kept my temps on the lower scale of what is alright for a betta. When i left for the day, i turned off the light and turned the filter back on. Tomorrow i'll check the temp when i get in, and if its steady, i'll turn on the light and unplug the heater and see how things go for the day.
I will probably turn the filter on from time to time to clean the water, but not leave it on all the time.