A heater I would not suggest is the EBO-Jager. It's not fully submersible like I thought it was, and although you have a separate controller, the temperature controller that's on this unit doesn't seem worth much. It says it can control the temp +/- 1 degree, but I have to set it 5 degrees cooler than what I really want, and then it's still +/- a few degrees. Of course, this may be an issue for most heaters. On the good side, it does have a pretty good design otherwise, looks like it'll last me, has an automatic shut-off if you don't submerge it far enough, and even though it's not fully submersible (I worry about the suction cups failing and it falling into my tank), it does seem to be pretty water tight (I've already dropped it into my mixing bucket once with no damage).