Omni-Akuatika Special Issue The 4 th KRIPIK-SciFiMaS 2022: 37 - 42 1 The Application of Chitosan as a Natural Flocculant Material to Chlorella sp. Abundance Dewi Puspaningsih * , Eri Setiadi, Lies Setijaningsih, Imam Taufik Research Institute for Freshwater Aquaculture and Fisheries Extention, Jl. Sempur No. 1, Bogor, West Java, Indonesia *Corresponding author: d_puspaningsih@yahoo.com Received 9 November 2021; Accepted 24 February 2022; Available online 18 April 2022 ABSTRACT Natural feed must be available in order to give high-quality seeds to support aquaculture activities. Chlorella sp. is a natural food source for fish larvae and zooplankton. Chlorella sp. is more effective and efficient when stored in the form of floc. The purpose of this research was to obtain an effective dose of chitosan for flocculation of Chlorella sp. The study used a completely randomized design (CRD) with 5 treatments and 3 replications, i.e A. 150 mg L -1 , B. 200 mg L -1 , C. 250 mg L -1 , D. 300 mg L -1 , E. 350 mg L -1 . The abundance of Chlorella sp. before and after flocculation measured as the main parameter. Water quality parameter such as temperature, pH, dissolved oxygen, total ammonia nitrogen, and nitrite function as supporting parameters. The results showed that the abundance of Chlorella sp. before flocculation increased from the beginning of stocking until the 6th day. The best results of the abundance of Chlorella sp. found in the C treatment (54.4-74.5%), then followed with B, A, D, and E treatments (31.2-55.1%, 22.8-51.2%, 19.0-45.6 %, and 13.3-44.6%) respectively. The most effective dose of chitosan in the flocculation process of fresh water Chlorella sp. was 250 mg L -1 with an abundance of 39.1x10 5 cells mL -1 . Water quality in culture media of the Chlorella sp. showed that the range of measured values were still within the optimum range. Keywords: Abundance, Chitosan, Chorella sp., Flocculation ABSTRAK Pakan alami harus tersedia agar dapat menghasilkan benih yang berkualitas untuk menunjang kegiatan budidaya. Chlorella sp. merupakan sumber makanan alami bagi larva ikan dan zooplankton. Chlorella sp. lebih efektif dan efisien bila disimpan dalam bentuk flok. Tujuan dari penelitian ini adalah untuk mendapatkan dosis kitosan yang efektif untuk flokulasi Chlorella sp. Penelitian menggunakan Rancangan Acak Lengkap (RAL) dengan 5 perlakuan dan 3 ulangan, yaitu A. 150 mg L -1 , B. 200 mg L - 1 , C. 250 mg L -1 , D. 300 mg L -1 , E. 350 mg L -1 . Kelimpahan Chlorella sp. sebelum dan sesudah flokulasi diamati sebagai parameter utama. Parameter kualitas air seperti suhu, pH, oksigen terlarut, total amonia nitrogen, dan nitrit berfungsi sebagai parameter pendukung. Hasil penelitian menunjukkan bahwa kelimpahan Chlorella sp. sebelum flokulasi meningkat dari awal penebaran sampai hari ke-6. Hasil terbaik dari kelimpahan Chlorella sp. ditemukan pada perlakuan C (54.4-74.5%), kemudian disusul dengan perlakuan B, A, D, dan E (31.2-55.1%, 22.8-51.2%, 19.0-45.6%, dan 13.3-44.6%). Dosis kitosan yang paling efektif dalam proses flokulasi air tawar Chlorella sp. adalah 250 mg L -1 dengan kelimpahan 39.1x10 5 sel mL -1 . Kualitas air di media kultur Chlorella sp. menunjukkan bahwa nilai terukur masih dalam kisaran yang optimum. Kata kunci: Kelimpahan, Kitosan, Chlorella sp., Flokulasi 1. Introduction Nowadays freshwater aquaculture activities are currently being carried out intensively. The availability of natural feed is needed to produce quality seeds in order to support aquaculture activities. Until now, natural food cannot be replaced by artificial feed because it contains digestive enzymes that make it easier for larvae to digest their food (Abdel-Ghany and Salem., 2019). The advantages of natural feed compared to artificial feed are that it is generally small in size so that it can be adapted to the larva's mouth opening, has a color that attracts the attention of the larvae, has a slow movement so that it attracts attention and makes the fish easier to catch it, naturally a feed that is usually eaten by larvae, its nutritional quality can be improved through enrichment, and can be cultivated intensively. Omni-Akuatika Special Issue The 4 th KRIPIK-SciFiMaS 2022: 37-42 ISSN: 1858-3873 print / 2476-9347 online Research Article journal homepage: http://ojs.omniakuatika.net http://dx.doi.org/10.20884/1.oa.2022.18.S1.977