I buy heaters on eBay from Top Dog Sellers or CLL pet supplies. I have had good luck with these, one did leak early on and was replaced. If you can cover the bottom and as many sides of your tank as reasonable with foam board you can get away with a much lower wattage heater than you would expect. I use a 200w heater in a 75g in my 45f garage to keep tank at 68 and a 25w(!) keeps a 54g corner round at 74f (room 68). (Note those are goldfish tanks.). I have similar eBay brand 25w in my 3g beta tanks. The cords to these heaters are short though so u know. I have a 25w Hydor in one tank which is also great. Had a name brand 300w which died a glorious death. Just saying, name brand isn’t always best.