I have seven discus in a 240 gal tank for about a year. this past week a couple of times a day a random discus will flip out darting back and fort wildly. i dont know why. i lost one discus because of this he darted into the glass and hurt its self were it couldn't recover. i dont get it, they eat fine come over to the tank when they see anyone. theirs nothing that i know of that spooks them. water is superb. oh and after there done darting after a minute or two its like nothing ever happened they eat and act normal. does any know whats going on or any ideas please comment.