I'm even considering going with a Aqueon Pro 50 for my SpecV...no matter what I do, my house is cooler than optimal for these fish at night and all winter. Looking at quite a few different (non-mini) heater packages, for a 5 gallon tank, if you need to get more 5 or more degrees over, you should move up to a 50 watt. The Pro appears fully submersible, I figure put it low on the bottom, and heat will rise, along with circulation from the pump should work for coldest times of the year.
I sent fluval an email asking if using a ball valve or by wrapping the inflow with a carbon filter would reduce the life of the pump. They said their engineers would get back to me. That was over a month ago. Love the tank, not so much the customer service.
How I reduced the water from pushing him around was using a silk plant and wrapping it around the in flow valve. My guy likes to rest on the out flow but there hasn't been any problems yet (probably because the water is reduced).
I had been using the Elite Prime square block shaped filter over the outflow nozzle...I switched to the long cylindrical Pre-filter, which is made of much finer foam. Wow, that brings things almost to a standstill with the motor on low. But it probably filters smaller things out of the water, which might help until this Mopani wood slows down on leaking tannins out.