the invention concerns a composite gel comprising an inorganic matrix containing a fibrous inorganic polymer in which an active organic compound is dispersed . the invention also concerns a device comprising the gel and a process for delivering a controlled quantity of active organic compound in an aqueous solution . the invention applies to the prevention of biological growth in aqueous solutions used domestically , agriculturally or industrially , in particular in the solutions used in photographic processing . figure of the drawing to be published with the abstract : none