I've got mixed views on hemp but boy do fish eat it. Spent quite a few summers watching them in clear rivers and the way the different species react is quite a sight.
As a loosefeed in midsummer it's often the only bait chub really go for on a heavily fished water I know, when even maggots start to spook the chub. They just take it oh so delicately yet so confidently if that makes sense, so using a matchstick float is lots of fun in low water, I've tried freelining fake hemp which works but even in the clearest water it's a sod to see. You think the chub are precise you should see the speed the dace hit the stuff. Because of seeing this I believe a lot of the missed bites when hemp fishing are often dace and bleak.
Whilst doing that the big roach can be seen picking single grains off the deck whilst the ones under a pound compete with the chub and dace, it could be why tares pick off the bigger roach as it gets them off the deck competing for a bait the smaller fish struggle with.
Barbel and carp just get in a frenzy over the stuff on the bottom but things do get messy unless it's clean gravel, another reason larger visible baits over the top work best, funny enough the barbel work in straight lines before returning to the bottom of the swim and working up again, if there's a group of them they will bounce over each other, twisting but usually facing upstream, you can see them sucking it all up before they repeat the whole process, carp on the other hand are picky when solo but in a group they get their heads down and will uproot anything in their path to get at the stuff. What's noticeable is the carp's feeding will be more sporadic whereas the barbel will spend longer hoovering away. When they are doing this the biggest thing that spooks them are their fins touching a tight line on the bottom, another reason float can out fish lead in clear water.
I've seen all the above duplicated with pellets as well and they are all observations from low clear summer levels, but that's when particles work best I guess.
Ps Fake hemp does work but is nowhere near as good as the real stuff, they can tell the difference