Your foam is doing what mechanical filtration is supposed to do. It trapped fines and clogged up when the capacity is reached. If the filter doesn't get clogged up, it is not doing its job as water is bypassing around the media. There is no short cut to good mechanical filtration. Either you have to change media frequently if the media area is small such as a single HOB, or you can delay changing media if the media area is large such as a sump system or using multiple HOBs. I hanged multiple HOBs in my heavily loaded 125g, and have to change all filter media twice a week. When it comes to mechanical filtration, it is the media surface area, rather than the volume that matters because once the top layer get clogged up, the remaining thickness of the media is no longer fully utilized.