Hello again Jeff,
Most tropical fish are comfortable in water heated to the 76 to 80 degree range, so you're within that range. If the water temp starts to approach 80, then you may consider setting up a small fan directed at the tank until you get a reliable heater. If you can position the fan so it blows across the water surface, that would be best. I have several large tanks in my basement and the temp stays a pretty constant 72 degrees, so I do need a couple of small tank heaters. It doesn't take much to raise and maintain the water temp a few more degrees.
"Fear not, my young apprentice. Just change the tank water."