I am all for doing things that will save me money but I would not skimp on my
ballast. The thing that you should think about is that the
ballasts that you can get a lowes and home depot may not have been designed to be used in areas of high moisture (ie. around your tank). I would personally not get
ballasts that were not made specifically for use around marine aquariums. If I were in your shoes I would look into the many brands that are on the market and determine which is better for your situation. I personally like Icecap and Hagens Glo systems.