I would imagine theres other smaller fish amongst them,
if thats the case just simply loose feed maggot & fish
caster on the hook. That usually seperates the chub catch.
If not just use small pieces of corn on top of crumb ground bait.
now heres a guy who can catch chub...lets.
For small chub use double maggot or worm section, if they are over a pound id go about it as you would normal chub but scale down a tad. Treble maggot, bread and worm i think would work
maggot and loose feed (maggot or caster)over the top, they will come up to feed , so I would space your shot and aim to catch on the drop later in the day. caster also works well. (but forget the bigger baits, if the fish are small.)
For stillwater chub id recomend that you regularly loosefeed maggots and fish caster on the hook! Aim to get the fish right up in the water and feeding confidently. Should get em goin its when they get big that they get difficult to catch