Not sure if your penguin has those black clips with the white bags you fill with your media.. I'd recommend getting the Eheim Substrat Pro Biological Filtration media. It comes in a box and you get enough of it, just fill your white sponge bags with the stuff. Basically the little balls in the media are the best spots for bacteria to grow and colonize. Then like every 2 months or so, take out the bags, dump all the media into a plastic bag don't wash the media or let them dry out. Wash out your bag and put the media back in and put it back in your filter. I know there are a few things to watch out for with those over the edge penguins. The biowheel is a gimic anyways and so are the media bags if you aren't using them. After awhile your biowheel will stop spinning like it did when you first turned on your filter. What will happen is one side of the biowheel will dry out and the other one will be wet, which will cause the wheel to never spin because it will be bottom heavy. In order for that thing to have some kind of use, it should be %100 wet and hosting benefical bacteria. If this happens just put the wheel in a ziplock bag with water in it and let it sit for a few days. I mean I just suggested putting the Eheim media in there, but in all actuallity there isn't enough media in there to do any kind of significant bacteria growth. But it's better then having charcoal or something else in there.
Bottom Line, the most of your bacteria in any tank is going to be in the gravel. The thicker your gravel bed the larger potential you have for having an even larger bacteria colony. Don't do crazy gravel vac water changes, because that's where your mojo is going to be growing and living. If your tank is truely cycled, anything that hits the floor should show signs of decay or be completely gone within 2-3 days. Including fish poop, dead fish, and fish food. Just make sure you're doing water changes to get rid of toxins.