A fish tank apparatus includes a plurality of fish tanks and water measuring apparatus. The water measuring apparatus includes a measuring member for detecting water parameter, and a switchable sample water diverting member having a plurality of inlets and at least one outlet. A central measurement conduit fluidically connects the outlet of the switchable sample water diverting member with the measuring member. A plurality of peripheral measurement conduits fluidically connect the fish tanks with the inlets of the switchable sample water diverting device, which is configured to selectively feed sample water from each one of the peripheral measurement conduits to the central measurement conduit to test the water in the fish tanks.
