I have a heater i bought from walmart labeled as a 30-60 gallon and it doesnt work to well. One day i will check the temperature and it will be at 73, the next it will be at 80. I need a good reliable Heater that will keep my tank at a steady 80-82 degress for a silver arowana. Im not sure if its how i place the heater, i have it upright and towards the filter. I was wondering if i place it sideways it will work more efficiantly?