The additive OPTIPHOS ® is a preparation of 6-phytase that is authorised for use in avian species, weaned piglets, pigs for fattening and sows. The applicant seeks for an extension of use of the product to finfish, at a dose range between 250 and 1,000 OTU/kg feed. The FEEDAP Panel concluded in a previous opinion that there are no concerns for consumer safety and no risks for the environment are expected from the use of the product as feed additive. Moreover, it was concluded that the additive is not a skin/eye irritant or a skin sensitiser, but has the potential to be a respiratory sensitiser. The Panel considered that the new use of the additive would not change the previous conclusions regarding the safety for the consumer, user and environment. The results of a tolerance study performed in juvenile rainbow trout (Oncorhynchus mykiss) showed no negative effects of the additive on the fish when offered up to 100 times the maximum recommended dose. Therefore, the Panel concluded that the additive is safe for the rainbow trout and extrapolated this conclusion to all finfish. The Panel evaluated three efficacy trials, two performed in rainbow trout and one in Atlantic salmon (Salmo salar). In these studies, the performance of the fish was monitored as well as phosphorus digestibility and phosphorus retention parameters. In the three trials, the performance and the phosphorus retention were improved by the additive at the lowest tested dose (in rainbow trouts at 250 OTU/kg feed and in Atlantic salmon at 500 OTU/kg feed). The FEEDAP Panel concluded that the additive has a potential to be efficacious in rainbow trout and salmon at 500 OTU/kg. The Panel extrapolated the conclusion to all finfish species.