Within the first year we had our Trex deck installed it started getting the black mildew spots all over. We tried a cleaner from Lowe’s but it didn’t do a thing. Then our contractor who installed the deck recommended Corte Clean. Within the first 5 minutes of cleaning the deck in the direct sunlight, the spots were gone! My husband and I couldn’t believe our eyes because we thought we’d never find anything that worked. We will be a customer for life and will recommend this product to all our friends who have Trex decking!