Custom Sealife made the T1 through T4 and now someone bought them out. I believe Jason carries these. They heat your water 2 to 4 degrees warmer than with other pumps. So why would you use a pump like this? Because there is no noise! If you have an office and the temp stays at around 70 degrees it is the best pump you could find. My boss has had his for seven years with not one problem and since he is so picky it is perfect because no noise. Panworld pumps are made by an ex-engineer of Iwaki's, but are better. Also when you use a submersable pump you are adding voltage to your tank, so will have to install a grounding probe.