This study aimed to analyze the effectiveness of Tegillarca granosa at different sizes and densities on remediating the water quality of intensive Litopenaeus vannamei shrimp and the impact on gill damage and mortality of the shellfish themselves. This research was conducted on a laboratory scale at the Bone Marine and Fisheries Polytechnic, Bone Regency, South Sulawesi Province, Indonesia. Observations were carried out in situ for 7 days. Water quality parameters were analyzed at the Research Institute for Brackish Water Aquaculture and Fisheries Extension. Gill histology observations were carried out at the Main Veterinary Centrer, Maros. The decrease in dissolved total organic matter indicates the effectiveness of the shellfish as filter feeders in absorbing organic matter, both particulate and suspended. Small-sized shellfish are more susceptible to damage from exposure to excessive organic and inorganic compounds, suspended and dissolved in the water, compared to the bigger ones. The deaths of shellfish are initiated by gill damage.