Ok, my latest thought/dilemma of the week. I have a 55 gallon long with an Emperor 400 and air bubbler. Glass top. Room temperature is low 70's. I have put the heaters positioned horizontally exactly in the middle of the aquarium on the back wall. I bought a cheap 200W tetra dialed heater and at the supposed 78 degree setting, the tank was only 77 degrees. I turn up the heater all the way, was still 77 degrees. So...I take it back and get another...same problem. Then, I go to lfs and buy a marineland stealth 250W, remove the tetra heather, set the new one on 78 degrees...tank is still 77. I put the heater on 80 degrees...still 77. I have used a professional cooking probed thermometer as well as a tank thermometer to verify. Any ideas? Would it be wrong if I keep increasing the heater temp to get to the 78 degree mark?