EXHIBIT (21) SUBSIDIARIES OF OSMONICS, INC. Percentage Ownership 100% VAPONICS, INC. A Massachusetts Corporation 100% AQUA MEDIA INTERNATIONAL A Delaware Corporation 100% AQUA MEDIA OF ASIA LTD. A Hong Kong Corporation 100% PORETICS CORPORATION A Delaware Corporation 100% OSMONICS ASIA/PACIFIC LTD. A Hong Kong Corporation 100% OSMONICS EUROPA, S.A. A Switzerland Corporation 100% OSMONICS INTERNATIONAL LTD. A Jamaica Corporation 100% OSMONICS INTERNATIONAL, INC. A Minnesota Corporation 100% OZONE RESEARCH & EQUIPMENT CORP. An Arizona Corporation 100% GHIA, INC. A Nevada Corporation 100% AUTOTROL CORPORATION A Wisconsin Corporation 100% AUTOTROL (FAR EAST) LTD. A Japan Corporation 100% AUTOTROL S.A. A France Corporation 100% AUTOTROL INTERNATIONAL SALES CORP. A Virgin Islands Corporation 100% AUTOTROL PTY. LTD. An Australia Corporation 100% MICROL SYSTEMS, LTD. An England Corporation 100% PETECO CORPORATION A Minnesota Corporation 50% NIPPON AUTOTROL K.K. A Japan Corporation