Probably one of the best sites for 99% of your questions, proved over the years. I ditched Matrix after a one year test and it did nothing. Knowing that is is just cheap pumice stone, and stone is not porous, nor is biohome or ceramic. You must have water flowing through your media to oxidize ammonia, not around it. Your K1 may be expensive and like that web site says, sponges and pot scrubbies have 10 times the surface area of any hard, non porous media. 30 ppi foam is nice but still clogs up in about 4 weeks. Better to use 10/20 ppi foam so it won't clog for about 4-6 months. I use only 10/20 ppi foam and pot scrubbies in my canister and only 10/20 ppi foam in my HOB's. Water has never been better. Best of all, I don't have to clean anything for months.