The only time the noise does stop is when I reduce the outlet flow, but by this point the flow is so little that it doesn't clean the tank properly.
Does anyone have any suggestions? The noise doesn't bother me personally, as the terrapins (turtles!) are in a shed outside, but I wonder if it bothers them? If I had to listen to it day and night I'd go mad! How good is their hearing?
Cheers,
Liam

