I'm not very familiar with that filter , but I can tell ya it would work until something else comes along.
I did exactly what your doing in a 12g flat back hex tank I had and I used a filter rated for like50-75g I think , but I slowed the impeller down by clipping 1/2 off 2 of the 4 fins adjacent eachother so to not throw off balance.
You won't use it as a filter no media is needed , only some good macro algae and perhaps a small sock of phosguard . The macro algae needs a light but doesn't need to be elaborate , I use cheato and it
Grows under most any lighting. I grow mine under one 15watt compact florecent curly q bulb , Philips brand but that doesn't matter also cheato doesn't go sexual like many macros so it won't die off on you , one though you could try is mounting a single led under the hobs cover so you don't have light scatter .
The whole idea with this setup is that the algae uses the nitrates and phosphate in the water for nutrition wile photosynthesis releases oxygen back to the water , also a larger hob gives added water volume .
If you decide to do this let me know and when you start cycling ill mail you a fist of my cheato full of pods and little micro starfish to get it started it grows really fast .
