A pet shop near me has some Red Sea Root Therm substrate heaters that have been sitting on the shelf for a long time, so he lowered the price on them. Are they worth resetting a tank to install, is this a good brand, are they still being made because when I tried to comparison them, they were generally on old webpages out of stock. His lowered price is good considering shipping if some of these other stores were not out of stock. One is for a 100 gallon tank, the other size for a 40, so if I did install them, should I use two of the larger size, or one large one small since that would be just under 150 gallons. He lowered the price of both sizes to the same figure, so there would be no cost difference, just concerned which would be the best configuration.