Just wondering but why would 80 degree's be a problem?
The reason i was wondering is because thru research it seems that most of the small characin's (tetra's) are recommended to be kept in 80-84 degree temps.
I personally was unable to keep my cardinals or my brass tetra's at temps below 84. I did notice that my flame moss has slowed in growth considerably since the temp raise from 74-76, but the tetra's have been doing well for a few months now.
I wish I could get 80 degree temps thru my filter so that i did not have to have a unsightly heater in the tank.