I have a question about my water temp. no matter what i do thewater stays at about 84 degrees. I had the heater set to 79 and the thermometer said the temp was 82 so i lowered the heater to 72 and it didnt lower it actually has gone up a few degrees. the fish dont seem to mind it? they are acting normal and eating regularaly and actually now my pleco poops a lot more. im not sure what to do to lower the temp in the tank? help plz