There is a need for standardised comparative data on the efficacy of aquaculture disinfectants to guide their use by farmers and health professionals, as well as Competent Authorities for authorisation or listing purposes. Towards this aim, two already available CEN (Comité Européen de Normalisation) quantitative suspension test standards for the evaluation of bactericidal and virucidal activity of disinfectants and antiseptics for use in the veterinary field were modified by using agents and testing conditions representative of aquaculture conditions. For evaluating bactericidal activity, BS EN1656:2000 was modified to test disinfectant activity against Aeromonas salmonicida subsp. salmonicida (ATCC 14174), Yersinia ruckeri (ATCC 29473), Carnobacterium piscicola (ATCC 35586) and Lactococcus garvieae (NCIMB 702927) for a contact time of 30 min and temperature of 4 °C. Interfering substance was used as described for dirty conditions in the standard (10 g l⁻¹ yeast extract plus 10 g l⁻¹ bovine serum albumin solution). The substituted organisms could be stored and readily resuscitated. They were not adversely affected by the assay conditions (except exposure to the disinfectant) and could be readily prepared as suspensions. Four example products, coded A–D, were tested using both methods (including a peroxygen system, a product containing a mixture of hydrogen peroxide and peracetic acid, an acidic iodophore and a Chloramine T containing product). The neutralisation-dilution method, preferred in the standard, was appropriate for all products. Although there was greater test-to-test variation at the higher end of effective dilutions, repeat testing gave reliable results for four products as bactericides. L. garvieae and C. piscicola were the most resistant bacterial pathogens tested, requiring concentrations between 0.1–0.5% of the four products tested to achieve 5 log₁₀ inactivation. For evaluating virucidal activity, BS EN 14675:2006 was modified to use infectious pancreatic necrosis virus (IPNV), Spjarup serotype, using the same products with testing conditions as for BS EN1656:2000. The acidic iodophore-containing product (C) gave rise to cell cytotoxicity problems with the recommended neutralisation dilution method for titration of remaining viral activity. The other three products were reliably tested for virucidal activity using the modified assay. A further assay modification for virus mixed with Product C involved membrane dialysis for 48 h following test exposure and neutralisation by dilution. This reduced cell cytotoxicity enough to allow titration of the remaining viable IPNV.