hi biscut, the 2 16watt spirals i used are working fine, no heat build up as the temp stays the same with them off or on, i think there about 6"away from water so no problems so far! i have had it setup now for 3 weeks with yelllows and tiger shrimp and plants, and eco complete with blk rock mixture. i leave it on about 8-10 hrs a day with no problems with algae yet. i only dose it once a week with trace iron and flourish,low doses though!! have an aquaclear 10 filter to, working good so far!