Cycle of concentration represents the accumulation of dissolved minerals in the recirculating cooling water. Steering controls included variable-ratio recirculating ball steering gear with optional hydraulic power assist. One of the drawbacks to recirculating aquaculture systems is the need for periodic water exchanges. PEX is suitable for recirculating hot water. The campus boasts one of Victoria's few indoor recirculating aquaculture facilities. Ozone is also added to recirculating systems to reduce nitrite levels through conversion into nitrate. Steering was power assisted, recirculating ball with variable steering gear ratio. W 45, which had recirculating oil lubrication. It is used at a level of 10 ppm in irrigation and recirculating waters. Rock wool is an inert substrate suitable for both run-to-waste and recirculating systems. Steering was recirculating ball system, with power steering optional. This conserves heat by recirculating it back to the body core. The steering column turns a large screw which meshes with nut by recirculating balls. Renovations included fabricated trees, rock work, and recirculating water. Variable-ratio power steering was standard of a recirculating ball type.