Chub are opportunists
Chub just love maggots, and continually spraying them into a chubby looking swim usually eventually gets them feeding. I've done it loads of times on rivers and stillwaters. While I'm trying to catch chub, I often catch lots of small fish which could be roach, rudd or perch usually. If this should happen, I see a chance to have some fun and witness the chub as it can be - a fearsome predator to the smaller fish in its domain. If it fits in its mouth it will have a go at it. I've seen this when lure fishing and had accidental chub captures on large lures like Rapala Super Shads.
When this is the case, I like to do something different and target the chub to take advantage of its predatory instincts. All I do is take off a couple of shots from my waggler set up so the float sticks well up in the water. I then hook a small fish near the dorsal and cast it back into the swim. It's a sort of mini livebaiting.
So many times a big chub has taken the small livebait even though I'm still spraying with maggots. I wonder how many small fish they eat on these occasions and we are not even aware of it. In the opening picture, three of the big chub took perch livebaits, and the others two red maggots.
Chub are not stupid though, and will exercise extreme precaution, so I'm usually using a size 14 hook to a 3lb hook link. It's so easy to scare the shoal, so after I catch one, I will spray maggots for a good ten minutes before making another cast.