next suggestion is depending on how big they are and how many you have...tweezers :] place food like a algae wafer that wont float away near their hole and BAM.
I also heard of traps such as a pvc
pipe, cover one end in something like saran wrap and the other side with a cap + small hole drilled into it (about the size of the worms youre trying to catch). Then place food inside and sink it to the bottom. You should have some without catching your other CUC. Havent tried it myself but the idea seems sound