I have 4 powerheads in my 50 gallon tank that have sponges affixed to their intakes, and that filters the water mechanically and biologically.
I've used sponges I found in the garage- from the 80's...
Perfectly preserved. I tried using sponges from Home Depot, but the modern sponges deteriorate after a week or so in the water. And I've heard that sponges you buy at the store contain chemicals that could harm aquarium life. But these sponges that use old school formulas don't degrade unless it's been in the sun. So they've been great for many months, and I rinse them through about once a week.
But, after adding a CO2 generator, the water chemistry changed. It got a little cloudier, string algae started to proliferate, and I noticed that the sponge filters got clogged must faster- I have to wash and rinse them every other day now. I suspect that the sugar or the yeast that comes up through the CO2 line is particularly good at clogging the tiny holes that make up the sponge.
So, I need to get a new sponge material. Given my design with the powerheads, does anyone have a suggestion about the kind of aquarium sponges I can use. But it's imperative that the shrimp that live in the tank are not harmed- the modified filter design should not endanger the shrimp.