Originally Posted by CrypticLifeStyle
Firstly good choice on heater. I've had them all, and the ebo Jaggers are by far the best hands down. For a 10 gallon a 50-75 watt will be fine, and both are 9.5" tall so it would be fine vertical close to the filter intake. I do not think they are submersible though if according to the box nor have I fully submerged mine, however the LFS I got mine from horizontally submerged theirs so it prob would be OK.
I've had a total of 4 heaters failed (not due to flow, just crap quality) on me 2 Marineland stealth 250watts, 1 Theo 300watts & a Chinese no-name 300watts unit. The only one that remained working after years is my Ebo-Jager, now Eheim-Jager. I would never use anything but a Eheim-Jager and recommend this product highly. If you've ever held one in the hand you'll immediately notice the build quality is excellent.
Now regarding your application the only issues I see is (1) the physical size of the Eheim-Jager as another member have noted (2) the lack of circulation to move the heater water from around the coiled
area due to the size of the tank- I assume lower flow.
If you didn't already know this the most important thing (other than build quality) for ANY heater is water movement around the coiled areas. The movement of the heated water from the heater what determines how accurate the water temp will be relative to what's set on the dial as well as reliability and why in-lines work so well. It's not because it's better, but it puts the heated surface in the perfect flow situation; something most do not do.
If you can provide a powerhead to move the heated water from the heated surface area this can work for you. If you cannot provide that type of flow I would not suggest anything over 150watts, even with that place it where it gets the most flow. If you have to move the dial past the labelled temp you want to achieve, e.g., 77 to 84 to achieve 77 - you have a flow problem.