Soiless Potting Media, 18 inches x 25 feet Misty Mountain. Adding dirt to an enclosed ecosystem creates multiple problems: dirt can be washed away by pond water or rooted out by Koi; and dirt can introduce â??badâ? bacteria to your eco-system. Misty Mountain solved most of those problems with the development of their SPMTM. Additionally, SPMTM leaves lots of surface area for nitrifying bacteria to grow on, especially when seeded with Bio-SeedTM.