Phages do not produce colonies. You need to prepare dilutions so that you can see individual plaques on a double layer plate.

Thanks Professor Michael J. Benedik for your suggestion. I will do that.

Hi, If I understand your question correctly, you're trying to apply bacteriological methods to viruses. It doesn't work. You need a host culture growing in the exponential phase. To obtain a virus subculture, You should transfer the PFU to the host liquid culture.