I am looking for suggestions for heaters to use to heat my 400 gallon tank. I have a no name 300 watt and a finnex 500 watt heater that I am using now. The Finnex just crapped the bed. It is less than a year old. What do you suggest? What have you had success with? Am I better off with 3 smaller heaters or 1 large and 1 small?