I am getting a 180 gallon 96Lx24Wx24H tank. I'm needing heaters and was thinking of getting two smaller heaters so if one fails they don't cook or freeze my fish. What strength heater do you recommend if I put two in the tank? I would think I would put one on each end? The room temp is about 68 all the time and I need the water to be 75-80. I've heard ehiem is good.