i think what xmas means is break the tank down completely. i would remove and rinse the gravel, scrub the glass, and then for good measure let everything dry out completely bone dry before restarting. if you want, you can fill the tank and gravel and nuke it with the peroxide to kill anything left. should leave an almost sterile tank to start with. as for the heater, if your going to replace it, go with 2 smaller ones. that way if one gets stuck on or off, it wont swing the temp up or down too drastically before you notice and can correct it. thats what i do on my sulawesi tank.