This project was performed on assigment of Vattenfall R&D in Älvkarleby. The project was a first step in evaluating whether bubble curtains with vertical tubes could be suitable for diverting fish from hydro power intakes into fish passages. To determine this, prototypes were constructed, where one was tested in still water and one in running water. The tests in still water were carried out in a large cylindrical tank and the tests in running water were carried out in Kungsr¨annan in ¨Alvkarleby. A number of test variables were developed to be able to vary the tests. These test variables were hole size, number of holes, tube center-to-center distance, air flow and water velocity. The tests were carried out without fish, but a number of indicators were developed to be able to compare and evaluate the tests. For the tests in still water, these indicators were the width of the bubble curtain created by a single tube and the horizontal movement of the air bubbles, to determine whether the hydrostatic pressure from the surrounding water had any effect on the appearance of the bubble curtain. For the tests in running water, the indicators were the bubble curtain density, the curvature of the tubes and the movement of the tubes. All experiments were documented using cameras and the results were then obtained through image processing in the software MATLAB. The results showed that the width of the bubble curtain created by a single tube varied between 12 and 34 cm for pressures between 0.5 and 2.0 bar. It was concluded that the hydrostatic pressure was of minimal significance for the appearance of the bubble curtain, at least for depths up to 1.95 m. For the tests in running water, the air flow rate and tube center-to-center distance was of the greatest importance for the bubble curtain density. The curvature of the tubes were most affected by the size of the holes and the movement of the tubes were most affected by the number of holes.