ABSTRAKSektor perikanan Indonesia sangat potensial dan mempunyai prospek besar dalam peningkatan devisa negara, salah satunya budidaya udang vannamei (Litopenaeus vannamei). Salah satu produk perikanan yang mengandung bakteri Lactobacillus adalah probiotik “Boster Bio Lacto”, tersusun dari bakteri Lactobacillus bulgaricus dan Lactobacillus casei. Bakteri Vibrio sp. menyerang udang. Pertumbuhan berdasarkan jumlah ukuran dan kuantitasnya. Fluktuasi pH, tingkat oksigen, temperatur, salinitas, kadar ammonia, serta bahan-bahan organik dapat sebagai penyebab stress pada udang dan memicu penyakit. Tujuan penelitian ini adalah mengetahui bagaimana efek penambahan Biolacto pada budidaya udang vannamei selama 30 hari terhadap kelimpahan bakteri Vibrio sp., kualitas air dan pertumbuhan serta penambahan dosis Biolacto yang tepat. Hasil penelitian menunjukkan bahwa pemberian Biolacto memberikan penurunan kelimpahan bakteri Vibrio sp. pada dosis 10 ppm dan 15 ppm dengan rata-rata 18,40 CFU/mL. Pertumbuhan tertinggi dosis 10 ppm dengan rata-rata berat 26,16 gram dan panjang rata-rata 52,4 mm. Kualitas air dalam kisaran normal. Kata kunci: Biolacto, bakteri Vibrio sp., kualitas air, pertumbuhan, udang vannamei (Litopenaeus vannamei)ABSTRACTThe Indonesian fishery sector is very potential and has great prospects for increasing the country's foreign exchange, one of which is vannamei shrimp (Litopenaeus vannamei) cultivation. One of the fishery products containing Lactobacillus bacteria is the probiotic “Boster Bio Lacto”, composed of Lactobacillus bulgaricus and Lactobacillus casei bacteria. Vibrio sp. attacking shrimp. Growth based on the number of sizes and quantities. Fluctuations in pH, oxygen levels, temperature, salinity, ammonia levels, and organic matter can cause stress to shrimp and trigger disease. The purpose of this study was to determine the effect of the addition of Biolacto on vannamei shrimp culture for 30 days on the abundance of Vibrio sp. bacteria, water quality and growth as well as the addition of the right Biolacto dosage. The results showed that administration of Biolacto reduced the abundance of Vibrio sp. at doses of 10 ppm and 15 ppm with an average of 18.40 CFU/mL. The highest growth dose was 10 ppm with an average weight of 26.16 grams and an average length of 52.4 mm. Water quality within normal range. This study recommends using Biolacto at the right dose because it can affect the abundance of Vibrio sp. bacteria, water quality and the weight and length of shrimp can grow well.Keywords: Biolacto, Vibrio sp. bacteria, water quality, growth, vannamei shrimp (Litopenaeus vannamei)