during and after a water change, my fish get spooked but they act normal, once i'm done. i've noticed that my oscars pig out on silversides and fill their mouths up so much that they go hide for a few hours or until they can digest a mouthful of cut up silversides. i think mine hide because they think that another fish will take a piece of silverside out of their mouths. my tire track tried to pull a piece of silverside out of the mouth of my florida gar. gars eat slowly and tend to move food in their mouths so that it will slide down their narrow throats. while he was moving the food around, my fast tire track tried to go for it.