Heating Problems..!
Hello Robertop,
I have some advice and please don't take it wrong. First if this is you're very first tank I would advise up-grading to a bigger one; bigger tanks are more forgiving and if problems should arise you have a bigger time span to react to the problem, and fix it.
I know tanks can be pricie, but a nice tank would be a 30 or even a 45 Gallon, believe you never stop learning when it comes to being an aquarist. Everything you will have depends on the size of tank you have. What kind of filter you are going to choose, heater, UGF (Under Gravel Filter), power heads, plants or no plants and this will be dictated by what type of fishes you wan't to keep in your tank; wheter is going to be a community or a species or even yet just an underwater garden.
Check your heater and make sure you have the correct watts/gallon of water you require, and check the basics, how strong your lighting is (watts) .