Those close up shots show your poret looks completely different than the stuff I have! even the cells are shaped different (like tight and granular). Is that 20ppi?
Ran into the same thing. Those pieces I posted about before are long gone. Turned into moon holy rock crumbles. I've been using the aquaclearr 110 foam blocks with great result. Very firm and easy to clean.Six months later, and the poret is decaying even more. I am not sun drying it any more but it is getting worse. Rather than catching debris, the foam is now creating its own debris.
On the hunt now for better quality foam.