I'm not familiar with what the penguins look like but in my HOBs I use biomax 50 from aquaclear. They are smaller ceramic rings that can fit in smaller spaces. I then fill the rest of the space with quilt batting. I got a 5lb box of quilt batting for about $12 and I've hardly put a dent in it.
I just rinse the quilt batting out with straight tap water to train the bacteria to live in the bio media. I replace the quilt batting if it gets too nasty or too clumpy after rinsing to put it back in.
I just rinse the quilt batting out with straight tap water to train the bacteria to live in the bio media. I replace the quilt batting if it gets too nasty or too clumpy after rinsing to put it back in.