Global aquaculture production has been growing at about 8% per year compensating for the stagnation of fisheries, and it is likely to become the main source of aquatic food for humans as demands continue to grow. This development in aquaculture is predicted to replace fisheries as intensive animal production has replaced the land based hunting. To satisfy this predicted demand plant based alternatives to fish meal (FM), the main dietary ingredient for fish production, will be needed. However, the use of such alternatives may affect the water quality which determines the fish health and production. This study hypothesized that replacement of FM with rapeseed meal (RM) as major sources of crude protein (CP) would not affect the water quality of fish tanks inhabited by common carp (fish).