You got lucky when you cast beyond the Carp and retrieved the fly back towards him. Probably only worked because he had stirred up enough mud that he couldn't really tell where the fly was coming from. It was just there. Remember prey does not move towards the predator! Always try to place the fly in front of the fish or a little to the near side. That way when you strip the fly, it will be moving away from the fish, like it is trying to get away.
In really clear water, they even spook away from a clear line. I have had them swim right up to the line, turn and follow the line, both towards me or away from me, but they will not swim under the line.
Watch for the cat tails or reeds to dance as they navigate through them. Cast into the cuts and pockets. Also watch for them to poke their snouts up through thick algie as they cruise along beneath it and take a little bite now and then.
BTW cruisers in a group are usually moving from one place to the next and will not eat but it's hard to resist not throwing a fly at them anyway. Try for the last one of the bunch.
If you really want to get serious about this, read the book "Carp on the Fly"