Ikan nila (O. niloticus) merupakan jenis ikan bernilai ekonomis dengan kandungan protein yang tinggi, rasa daging yang enak dan khas, sehingga permintaan benih ikan nila menjadi tinggi. Permasalahan utama dalam pemeliharaan benih ikan nila adalah kematian benih akibat kondisi lingkungan yang berubah-ubah serta membuat kualitas air menurun dan menyebabkan benih ikan nila stress, mudah terserang penyakit bahkan mati sehingga diperlukan penggunaan teknologi sistem resirkulasi. Komponen penting dalam sistem resirkulasi adalah filter contohnya bioball sebagai media pertumbuhan bakteri. Tujuan dari penelitian ini untuk mengkaji kepadatan dan morfologi bakteri pada sistem resirkulasi budidaya ikan nila (O. niloticus) dan mengkaji korelasi hubungan keberadaan bakteri terhadap kualitas air. Metode penelitian ini menggunakan metode observasi dengan titik sampling pada wadah filter dan kolam pemeliharaan selama 28 hari. Kualitas air yang diukur suhu, oksigen terlarut, pH, amonia, nitrat. Perhitungan kepadatan bakteri dengan metode TPC, pengamatan morfologi koloni bakteri dilakukan secara makroskopis dan mikroskopis. Data yang diperoleh dianalisis secara deskriptif dalam bentuk tabel dan gambar. Hasil penelitian diperoleh bahwa selama penelitian menunjukkan kenaikan jumlah kepadatan bakteri, yaitu wadah filter cenderung lebih tinggi dibanding kolam pemeliharaan. Hasil pengamatan morfologi koloni bakteri makroskopis memiliki bentuk Round (bulat), tepi koloni Entire (rata) dan warna koloni putih. Pengamatan morfologi koloni bakteri mikroskopi semua isolat termasuk gram positif serta bentuk isolat coccus dan bacill. Kepadatan bakteri menunjukkan korelasi kuat searah terhadap pH, oksigen terlarut pada kolam pemeliharaan, amonia dan nitrat pada kolam pemeliharaan. Kepadatan bakteri berkorelasi kuat terbalik terhadap suhu. Kepadatan bakteri tidak berkorelasi terhadap oksigen terlarut dan nitrat pada wadah filter.

Kata Kunci: Jumlah Bakteri, Kolerasi, Koloni Bakteri, Kualitas Air

Parrot fish (Oreochromis niloticus) is an economically valuable type of fish with high protein content, a delicious and distinctive meat taste, so the demand for the fish seeds is high. The main problem in raising parrot fish seeds is the death of the seeds due to changing environmental conditions which causes water quality to decrease and causes the seeds to become stressed, susceptible to disease and even die, so it is necessary to use recirculation system technology. An important component in a recirculation system is a filter, for example bioball as a medium for bacterial growth. This research aimed to examine the density and morphology of bacteria in the recirculating tilapia cultivation system (O. niloticus) and examine the correlation between the presence of bacteria and water quality. This research method used an observation method with sampling points in filter containers and maintenance ponds for 28 days. Water quality was measured by temperature, dissolved oxygen, pH, ammonia, nitrate. Calculation of bacterial density with method TPC, observation of the morphology of bacterial colonies was carried out macroscopically and microscopically The data obtained was analyzed descriptively in the form of tables and figures. The research results showed that during the research the number of bacterial densities increased, namely the filter container tended to be higher than the maintenance pool. The results of observing the morphology of macroscopic bacterial colonies had a shape Round (round), edge of colony Entire (flat) and white colony color. Observation of the morphology of bacterial colonies by microscopy of all isolates including gram positive and other forms of isolates coccus and bacill. Bacterial density showed a strong unidirectional correlation with pH, dissolved oxygen in maintenance ponds, ammonia and nitrate in maintenance ponds. Bacterial density was strongly inversely correlated to temperature. Bacterial density did not correlate with dissolved oxygen and nitrate in the filter container. Keywords: Number of Bacteria, Correlation, Bacterial Colonies, Water Quality