I saw this water heater is that the one you were talking about? Also it mentions that 300W will heat up to 159-265 gallons of water, really? Also if I can place it in my sump I might as well get this.
Not familiar with that model. These below are rock solid heaters.
JAGER TruTemp Aquarium Heater - Eheim
Fully submersible aquarium heater with TruTemp technology from Eheim. Precise temperature control: 65-93° F Made from shatter-proof laboratory glass TruTemp technology - ability to calibrate the heater for precise temperature Easy calibration to ±2ºF Run dry protection with Thermo safety...
www.bulkreefsupply.com