Judul: The periphyton growth on raffia rope substrate that is potentially utilized as natural feed in nile tilapia (Oreochromis niloticus) seed rearing environment
Abstrak: Limbah pendederan ikan nila terdapat kelimpahan nutrien yang mampu dimanfaatkan oleh perifiton. Pertumbuhan dan perkembangan perifiton perlu menggunakan substrat yang baik seperti substrat organik dan anorganik. Penelitian perifiton secara langsung pada wadah budidaya dengan menggunakan jarak dapat mengoptimalkan manfaat nutrien yang terbuang. Hal ini mengadopsi pada pola penanaman dengan menggunakan jarak tanam rumput laut. Perbedaan jarak tanam dapat berpengaruh terhadap laju pertumbuhan, sedangkan panjang pendek pada tali dapat mempengaruhi luas ruang dalam penyerapan nutrien. Penelitian ini bertujuan untuk mengetahui pertumbuhan perifiton pada substrat tali rafia dengan jarak tanam berbeda yang berpotensi sebagai pakan alami di lingkungan pendederan ikan nila (Oreochromis niloticus). Ikan nila yang digunakan berasal dari Institut Pertanian Bogor dengan berukuran 3,71±0,99 g dan 4,34±0,63 cm. Ikan nila dengan padat tebar 20 ekor m3 dipelihara di kolam (20 × 10 × 1,5 m). Kolam pemeliharaan terdapat 9 hapa (100 × 100 × 50 cm) yang digunakan untuk penempatan substrat. Penelitian ini menggunakan rancangan acak lengkap (RAL) dengan tiga perlakuan dan tiga ulangan, masing-masing adalah jarak tali rafia 15 cm dengan 25 substrat (TR15), jarak tali rafia 25 cm dengan 9 substrat (TR25), dan ketiga jarak tali rafia 35 cm dengan 4 substrat (TR35). Hasil penelitian ini menunjukkan bahwa jumlah jenis, kelimpahan total, indeks keanekaragaman, indeks keseragaman, dan indeks dominansi pada perlakuan TR25 (jarak 25 cm) menunjukkan hasil terbaik. Perlakuan TR25 berbeda nyata (P<0,05) dibandingkan TR15 dan TR35. Kandungan proksimat perifiton sebesar protein 33,45 %, BETN 4,06 %, lemak 19,03 %, serat 11,81 %, air 10,00 %, abu 31,74 %, dan klorofil-a 9757,793 µg/L. Perifiton yang teridentifikasi diantaranya kelas Cyanophycea terdapat 4 genus, kelas Bacillariophyceae, kelas Chlorophyceae, kelas Protozoa dan kelas Rotifera. Hasil penelitian menunjukkan perifiton didominasi oleh Chlorophyceae dengan memiliki kemampuan beradaptasi lebih cepat dan baik di suatu perairan. Genus Chlorella yang kaya akan nutrisi dapat berfungsi sebagai pakan alami yang membantu pertumbuhan pendederan ikan nila. Hasil pengamatan parameter kualitas air menunjukkan bahwa kualitas air masih dalam batas toleransi pada pendederan ikan nila. Berdasarkan hasil penelitian ini dapat disimpulkan bahwa substrat tali rafia dengan perlakuan TR25 menghasilkan pertumbuhan perifiton terbaik, dengan hasil identifikasi tertinggi pada kelas Chlorophyceae dan genus Chlorella yang berpotensi sebagai pakan alami di Lingkungan Pendederan Ikan Nila (Oreochromis niloticus)., Nile tilapia seed rearing waste has abundant nutrient that can be utilized by periphyton. Growth and development of periphyton needs better substrates, namely, organic and inorganic substrates. Periphyton study performed directly into the culture tank to optimize the nutrient waste utilization. This condition can be performed by the planting pattern based on the seaweed planting distance. Different seed planting distances influences the seaweed growth and rope length influences the space area for nutrient absorption. This study aimed to identify the periphyton growth on raffia rope substrate that is potentially used as a natural feed in nile tilapia (Oreochromis niloticus) seed rearing environment. The nile tilapia fish used were obtained from IPB University with 3,71±0,99 g and 4,34±0,63 cm size. Nile tilapia with 20 fish m-3 were reared in a pond (20 × 10 × 1,5 m). The rearing pond had 9 rearing nets (100 × 100 × 50 cm)
Keyword: growth, Oreochromis niloticus, periphyton, planting distance, raffia rope substrate

Judul: The evaluation use coconut leaves substrates with different area to increase media quality and production of Tilapia Oreochromis niloticus base on periphyton.
Abstrak: Tilapia Oreochromis niloticus is one of the superior products in aquaculture production. Periphyton can be consumed or utilized by microorganisms in the aquaculture and improve the water quality. Therefore, perifiton can improve the all system efficiently. This study aims to analyze the productivity, to assimilate the N and P by periphyton on coconut leaf substrate, evaluate the performance of the periphyton on coconut leaf substrate in improving the tilapia’s media quality and production, and determine the extent of the coconut leaf substrate that produces a maximum output performance. The experiment was conducted in the fisheries of IPB Diploma Program, for 3 months with a two-stage study. Phase 1 study used 3 pieces 3 m x 1.5 m x 1 m tubs equipped by 1.5 m x 1 m x 1 m net. Tilapias were stocked as many as 100 tails per tub. 6 (six) substrates in the form of 40 cm x 30 cm woven palm leaves were placed vertically. Phase 2 study used 12 tubs. The extensive treatment of coconut leaf substrate became a study treatment comprising of control tub without substrate (A), tub with 0.72 m2 substrate (B), tub with 1.44 m2 substrate (C) and tub with 2.16 m2 substrate (D). 300 tails of tilapia were stocked in each treatment. In the phase 1 study, the increase of periphyton biomass in basin 1 until the end of the study was 0.8 g/m2 per day. The process of Periphyton formation in waters was strongly influenced by sunlight, organic matter and nitrification process from waters. Proximate analysis results of 41.72% protein periphyton makes periphyton to be one of very good natural food sources. Constituent species composition of periphyton on of coconut leaf substrate is dominated by 1617.12 ind/L Chlorophyceae, 568.8 ind/L Cyanophyceae, 190.08 ind/L Bacillriophyceae, 24.48 ind/L Euglenophyceae much as, and 28.8 ind/L rotifers. The magnitude of Chlorophyceae indicates that the bacterial/organisms periphyton constituent are autotrophic, it is supported by the results of a chlorophyll of 30.08%. Phase 2 study generated the daily growth rate, survival, feed conversion ratio, protein retention and fish productivity which statistically significantly different (P <0.05). Fish biomass treatment A (0) is 11.67 kg, treatment B (0.72 m2) is 11.98 kg, treatment C (1.44 m2) is 13.76 kg, and treatment D (2.16 m2) is 14.58 kg. The amount of fish biomass in treatment D (2.16 m2) increases the lowest feed conversion value. Coconut leaf substrate can produce periphyton with a dry average weight of 34.41 g/m2, with the ability to assimilate N of 5.5%/m2 and P of 12.67%/m2. It is also able to maintain a constant low and appropriate ammonia for tilapia’s life and able to increase the production by five times of the initial biomass. The best extent of coconut leaf substrate to produce the red tilapia production is 2.16 m2.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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