I know the ideal temperature should be in the high 70's but I'm not getting there. My Eclipse 12 tank is consistently above 80* F - usually around 82*. I've used both a Coralife digital and glass thermometer so I believe the numbers. I've unplugged the heater and turned off the lights to see if that was affecting the temperature. They do to some extent because the temperature does rise a bitwhen they are on but with them off, the temperature stays up there. I've also tested my 30 gal goldfish tank that has low wattage light and no heater. Its temperature is about the same 80*. So, I'm thinking that I'm stuck with high temperature water. FWIW, the house temperature is set for 78* during the day and 80* at night.