How Often to Change Water for Crucian Carp?

Crucian carp water changes depend on container and season: in small containers change every 3 to 4 days in summer and every half month in winter. In large ponds or tanks with water hyacinth, lotus, or water lily to regulate quality, no changes may be needed. Tap water is fine, but first air it in sunlight for 2 to 3 days to remove chlorine, which otherwise harms or kills the fish.