I know goldfish and koi can pick up sound and vibration through their inner ear and skin, but I was wondering whether a rather loud submerged water pump could be causing my fish stress. My pond is just 1000 gallons so they really can't get away from it even though it is contained in a bio-filter box. Here's the thing... this pump has been in my pond for several years now, but ever since I changed it way back when, the fish have seemed to have become less active and not feeding as well as before the pump swap. It has taken me this long to wonder if this pump could be the reason. I am going to change it out anyway, but has anyone had this dilemma?