Fishways are frequently expensive to construct and the designs of proposed structures are commonly based on knowledge gained from existing structures, assuming that structures that allow passage of the species of interest exist. Developing an apparatus that allows rigorous testing of fishway structure designs prior to the construction of structures in the field could reduce the reliance on a “build it, monitor it, does it work?” approach, thus saving limited resources. Such an apparatus would also allow testing of the response of target fish species to design parameters (e.g., slope, roughness elements, water depth, etc.). As part of a larger project evaluating the performance of rock ramp fishway designs for fish native to the U.S. Great Plains, we designed and built a 9.1-m long x 1.4-m wide indoor research flume at the Colorado State University Foothills Fisheries Laboratory and installed a 6-m long experimental rock-ramp fishway within the flume. The flume can be adjusted from 0 to 10% slope, and incorporate curved sections from 45° to 180° in 45°-increments to allow testing various fishway configurations. Fish movements within the flume are tracked by an array of four dual-mode (full duplex/half duplex) PIT tag antennas. Flows up to 0.10 m3/s (3 cfs) are recirculated through the flume with a 15-hp pump; water temperature is controlled by a heater and chiller and can range from 10°C to over 25°C. Lessons learned during the design, construction, and operation of the flume are discussed in the poster.