If it clogs, then the water wouldn't be passing through the biological filter, so you'd see ammonia or nitrite spikes. I've had biomax in the top shelf of my Fluval 404 for 1.5 years and the water is still perfect with no reduced flow.
One thing I don't like about Penguin filters is that money sink replaceable filter. Once you realize you can rinse it out and use it for 3 months instead of one, you are saving a lot of money, but....Penguin probably doesn't like it.