I want to update on my 2nd heater that I got. It's a 50W and I put it in my 5 gallon with the babies. It works just as consistently as the 25W one, never varies a single degree in temperature. Even though it's only 64F in my house right now I can go to bed and wake up and it will be the exact same temperature - and it gets cold in here at night now! Only issue is, it's off by exactly 3 degrees. It's probably just this particular unit I have as I really believe that they have excellent quality products. I plan on keeping it and using it for as long as I can - it has a 3 year warranty so as long as it keeps holding the temperature consistent, I'll keep it in use.
Also, I still haven't heard anything back from my inquiry to them about why they can't be installed sideways. I'll definitely post again when I do :)