If your students are still struggling with webbed plates, particularly for low-yield or small plaque phage, we've had good luck (1) increasing the incubation time of bacteria + phage before making plaque plates to allow a lysis cycle (I'm using 1h instead of 15 minutes with globi as host, your timing may vary) and (2) dropping the top agar concentration in PYCa to 0.2-0.3% *by diluting with phage buffer* - this also provides 2.5-5% glycerol, which can help increase plaque size (Santos, Sílvio B., Carla M. Carvalho, Sanna Sillankorva, Ana Nicolau, Eugénio C. Ferreira, and Joana Azeredo. 2009. “The Use of Antibiotics to Improve Phage Detection and Enumeration by the Double-Layer Agar Technique.” BMC Microbiology 9 (1): 148. https://doi.org/10.1186/1471-2180-9-148.)
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