swamp cooler media (media/air filter.... the plastic kind obviously, not the straw/paper stuff) is even better than scrubbies imo.. 25"x25"x1" sheet is around $4.. its hit or miss with homedepot/lowes but HVAC supply houses always have it and in several different densities... i use a combination of scrubbies and swamp cooler media... the only kind ive found thats not reccomended for use in fishtanks is like $12 for a 25"x25"x1" sheet