I'm using a 3 way swivel for an average size moving river with a casting sinker...what is the minimum size sinker I'd need? I'd be catching freshwater drum, bluegill, etc...and would a bank sinker be better so it doesn't move around?

13 hours ago, Novatoad said:

I'm using a 3 way swivel for an average size moving river with a casting sinker...what is the minimum size sinker I'd need? I'd be catching freshwater drum, bluegill, etc...and would a bank sinker be better so it doesn't move around?

Going to depend a lot on current speed, bait size, bottom composition, line size, cast length, and various other variables. 

When I'm fishing the rivers around here for catfish, it takes from 1oz, to 8oz to hold a bait down. 

welcome to the forum! @Bluebasser86 is spot on.  Fishing for catfish on rivers here in PA, anything from 1/2 oz on up has a place depending upon bottom composition, depth, river level/flow/current, etc. A slip sinker also has a place on a river versus a three way swivel, and if I'm fishing the bottom with live bait, I generally prefer it in most cases because fish aren't feeling the weight when they take the shiner/helgramite/etc.

I have been using 1oz. pyramid sinkers. Heavier than that there is a much bigger splashdown which can spook fish. The shape of the sinker helps it hold not just the mass. Of course we don't know everything about your river's current so this is just an idea.