I'm kinda new and setting up a 28 gallon freshwater tropical tank. I've read that some people suggest using two lower watt heaters so that you A) have a back up if one stops heating and B ) so that if one fails and gets stuck on heating mode, it will have a hard time overheating the tank by itself. Has anyone done this? Results? If you recommend this dual heater setup, what size/wattage heaters would make sense for a 28 gallon?