you probably need at least 4 powerheads for that big a tank. my friend has a 75 gallon and he has 4. my little 37 gallon is pushing 2 by itself and i'm almost sure the current from one goes all the way from its end to the other end of the glass hahaha.. good luck.. btw, i am always looking at the glass too.. or sitting up in the middle of the night with a flashlight looking at the night time creepy crawlys that come out
have fun, gl!