You don't need a skimmer on the bio-cubes, they don't even come with one. I used to run two of them. One with a media rack and one without - couldn't really tell the difference honestly. In the end it all comes down to the same basic principles of good housekeeping and planning. There are some great threads out there with some modifications you can do to improve flow or add a light on the back to grow cheto, etc. Both of mine I retrofitted the lights with LEDs, swapped the return pump to something more powerful, removed the media cartridge, bio-ball things, removed chamber 1 false bottom, and again in first chamber removed the plastic tab to even out a single level overflow. Other than that one had a media basket that I would run purgen from time to time and chemi-pure.
Good little tanks, built like a truck, and with proper lighting can hold just about anything. Great nano tanks in my opinion that don't require a lot of day to day maintenance other than sitting back and enjoying.