I've been using a couple of Hydor ETH inline heaters for almost a year now and couldn't be happier. I like keeping the equipment out of the tank so these are great. Plus you don't ever need to worry about cracking one during a water change because they remain in contact with the water. I can't say for sure, but I seem to remember reading somewhere that because of their thin film heating element that they are not subject to cracking anyway. Lastly, the heat my water very quickly after a water change. Just my opinions anyway