I recently ordered a heater from bigalsonline.com for my tank. I have a 55 gal. The heater i ordered is only 150 watts, but says on the page for 40-60 gal tanks. I have read that you should go by 3-5 watts per gallon which would put my need at around 250-300 watts. Is this heater going to be sufficient or should i send it back for a bigger one?