Designed to optimize the performance of probiotic bacteria, the TWC block features a large internal surface area that supports bacterial colonization and biofilm formation. Bacillus species are foremost among the primary colonizing bacterial genus. B. subtilis and B. licheniformis in Pro4000X have been determined to readily colonize the blocks. They produce potent enzymes that degrade organic matter and enhance fish and crustacean microbiomes, which can reduce the levels of many bacteria, including potential pathogens. In addition, the Bacillus colonizing the TWC Block converts natural oils from feed and feces into amino acids, lowering surface tension and improving oxygen levels in the water.