The protocol provides an inexpensive, rapid (30 min) and reliable technique for obtaining counts of viruses and prokaryotes simultaneously. The method is from:Patel A, Noble RT, Steele JA, Schwalbach MS, Hewson I, Fuhrman JA.Virus and prokaryote enumeration from planktonic aquatic environments by epifluorescence microscopy with SYBR Green I. Nat Protoc. 2007;2(2):269-76.Please see the full manuscript for more details.