I keep my big tank 10-16 inch bass at 81. I have had heater failures where the tank dropped to 76. The fish were ok but you could tell they slowed down. When they are new 85-87 is good. I do run the growout at 82 also and all is fine but they only eat prepared foods. Don't feed live food, it can be fun but get them on blood worms, krill, silversides or better yet pellets as soon as possible. I feel this is the #1 cause of ick when bass are young. A little kosher salt is a great preventative too.