I've never fished a still water with barbel present but I have had lots of chub in still waters. I used to fish an old stone quarry when I was a kid and it held some very nice ones. The quarry was spring fed and also had a small inlet, sort of a decent flowing field ditch and the outlet was a lovely pristeine stream! Maybe it was because of the stream inlet and outlet that the chub bred as they did because they were present at all stages of growth. Even though this was when I was a youth I still remember it all clearly and the chub did put up a decent scrap, but not so good as when I caught chub in the river. I remember as soon as I hooked the larger ones which was always way out in the middle of the place ( and only in the heat of summer on the drawn out evenings) they would instantly dive for the cover of sunken cars about 40 or more foot down! The only way I could catch those larger fish was with floating caster or wasp grub and even though they were rarely fished for they were very hook shy. I remember meticulously hiding my 20's hook in casters and then squeezing the caster just enough to make it's insides come out, allow it to fill with air and then the white insides would seal the hole made by the hook and it floated perfectly. I had to use as light a hooklength as possible also so as to fool the chub into sucking it in. They where so shy I would have to catty out a handful of casters, then quickly cast my set up out as close to the centre of the freebies and lie down like a commando so the fish wouldn't see me!
I'd rather see barbel in still waters than wels catfish!