Barriers to fish passage such as dams, weirs and road crossings are a key threat to native freshwater fish. Fish need to move for many reasons including, breeding migrations, maintain population diversity, access refuge areas during drought and to re-establish in areas following disturbances.. A vertical slot fishway was constructed in the ACT on the Casuarina Sands Weir on the Murrumbidgee River when the weir was replaced in 2000 but it has been unclear whether it is effective or not. Funding from the Murray Darling Basin Authority’s Native Fish Strategy facilitated a trial of fish passage through the fishway. The project included the installation of a PIT array on the fishway and the capture and tagging of over 100 fish from four species. 50 fish (41 carp Cyprinus carpio and 9 golden perch Macquaria ambigua) were placed in the lower section of the fish way and their assent monitored by the PIT array. A number of problems were encountered particularly in regards to high laminar flow velocity, lack of fish motivation and head loss at the entrance to the fishway. A number of solutions to these problems were trialed. By placing the fish in the first cell and installing a baffle in the entrance slot flow velocity and turbulence in the fishway were reduced and 100% fish placed in the fishway achieved passage upstream. The results indicate that the fishway needs modification to operate effectively at low flow levels.