Totally amplitude of the wave will be around 1 1/2 inches that is down 3/4 " and up 3/4 of an inch from stable water level. Hope that helps. Seems to vary on tank design and rock formations a bit but it aint gonna be a tsunami, I have yet to see a commercial designed tank that overflows. At worst, sometimes when I try to move my magnetic cleaner aorund the end, if it times perfectly with the wave I will get a small splash over. Nothing real significant, a paper towel to clean the glass. Does that help?