If I can't get them going off the top on floaters I've been doing very well with zig rigs often in conjunction with a high-attract bait such as a flouro boilie or a big bunch of maggots. Finding the patrol routes between the shallows (used during the day) and the slightly deeper water (that is favoured at night) has been key for me. A couple of zigs presented on these patrol routes have picked up bonus fish when it seems nothing is going to feed.
Evenings and early mornings have been the most productive though, fishing tiny, out-of-the-way margin swims that aren't normally fished using just 1 or 2 rods usually slack lined or back-leaded, leadcore and heavy in-line lead. Baiting for a few days prior to fishing these margins has also helped, the carp get used to finding food there and feel safe eating it.