My red devils recently started doing this head shaking thing.I know it can be breeding behavior. But nobodies paired. I was thinking terrortorial. Just seems weird there doing it and not trying to pair. 3 red devils ,180gal,temps @ 82,one 4in, one 5in,and one 8in.Dont know the sex.Im about to do a water change and will post the results later.Its usually spot on though. I know there living situation may have to change do to the aggressive nature of the type of fish. Any input would be great.