Love fishing for Crucians, the only problem is all the farm ponds I used to catch them in have been filled in, stuffed with carp and goldfish or Cormoranted to death.
Used to do well with a small bait fished dead depth, dotted right down float next to cover. Feed LITTLE and Often. If using ground bait I would only put in a thumbnail sized ball at a time.
I'm the same, I haven't caught one for quite a few years, all the waters that I knew held them, have all been over stocked with various types of carp, including the brown goldfish, and now finding a true crucian around here, is like the proverbial rocking horse rubbish. I have heard of a couple of small ponds that have been recently stocked with true crucians, but they need a few years to grow on.