I've had two tank-raised true percs for about three weeks.  At night, they always act weird like that and get real motionless... sleep I guess.  During the day, they don't get too crazy and act pretty fearless of me.  I've heard tank-raised are quite a bit less scared.  They never eat the flakes I give them though.  They love some pellets better than anything I've tried.
I have a 24 aquapod and changed my stock with a maxi-jet 1200.  It does seem to be more heat than the stock.  Right now, my tank runs 79-83.  I actually need to set my heater to keep fluctuations down, but it hasn't been a problem yet.  It never gets above 82 when I leave the feeding lid open during the day.
But yeah, heat in the cubes is a huge problem.