Owner's Acorn Floats are an excellent choice for fishing moving water. Their shape makes them very stable, which is wanted while fishing slightly turbulent water. The shape also makes them a much better choice than the Nakazima Ball Floats or the Owner Top Floats. One BB shot will be sufficient so that only the red top of the float is above the surface. Rigged that way, it will be buoyant enough that current differentials will not pull it under, but a fish will feel very little resistance when it takes your bait or fly.
The floats in stock are the 40mm size, not the 55mm size shown in the image.