I have a 90 gal reef tank and can't keep a heater alive for 16 mos. I have used Gen-X, Won, and Proheat and all die within 8-16 mos. I have used a single 500w, dual 250w's, and now a single 350w. My heater is in the sump and never becomes uncovered. Any suggestions?? What brands have you used and been happy with??