I have a small fish tank and it is heated by a built-in lightbulb at the top. About 30 minutes ago, I turned it off because its nighttime. I checked on it like a minute ago it was still hot. But just in case, I wanted to make a heater, since its too late at night to go to the store and buy one. For now, I'm just using the heat that came off the lightbulb but I just want to be sure that my betta gets enough heat. (the lid is still really hot! ouch!!)
What are heaters made of, first off??? RAWRZ HELP!