Judul: Effect of Nitrifying Bacteria on the Nitrification Performance of Koi Fish (Cyprinus rubrofuscus) Rearing Without Water Change
Abstrak: Pencemar yang cukup banyak dan berbahaya pada akuakultur adalah senyawa nitrogen yang sering ditemukan diantaranya total amonia nitrogen (amonia dan amonium), nitrit, nitrat. Metode yang umum digunakan dalam mengurai senyawa tersebut adalah bioremediasi dengan memanfaatkan mikroorganisme sebagai agen pendegradasi. Penelitian dengan menambahkan takaran bakteri nitrifikan yang berbeda dengan empat perlakuan K (0 mg L-1), A (7,5 mg L-1), B (15 mg L-1), C (30 mg L-1) dan tiga ulangan memberikan respon yang bervariasi terhadap kinerja nitrifikasi. Tujuan penelitian ini menganalisis pengaruh takaran bakteri bioremediasi nitrifikan dengan dosis berbeda terhadap kinerja nitrifikasi selama pemeliharaan ikan koi (Cyprinus rubrofuscus) tanpa pergantian air. Hasil uji memberikan kesimpulan bahwa kinerja nitrifikasi tidak berbeda nyata pada setiap perlakuan dengan melakukan uji konsentrasi TAN, nitrit, dan nitrat. Parameter lain memberikan penjelasan bahwa perlakuan C (30 mg L-1) menghasilkan rasio konversi pakan dan pertumbuhan bobot absolut terbaik 2,61 ± 0,34 dan 0,29 ± 0,04 g dan berbeda nyata terhadap perlakuan K (0 mg L-1)., Pollutants that are quite numerous and dangerous in aquaculture are nitrogen compounds that are often found, including total ammonia nitrogen (ammonia and ammonium), nitrite, nitrate. The method commonly used to break down these compounds is bioremediation by utilizing microorganisms as degrading agents. Research by adding different doses of nitrifying bacteria with four treatments K (0 mg L-1), A (7.5 mg L-1), B (15 mg L-1), C (30 mg L-1) and three Replications gave varying responses to nitrification performance. The aim of this study was to analyze the effect of different doses of nitrifying bioremediation bacteria on nitrification performance during rearing of koi fish (Cyprinus rubrofuscus) without water changes. The test results concluded that the nitrification performance was not significantly different in each treatment by testing the TAN, nitrite and nitrate concentrations. Other parameters provide an explanation that treatment C (30 mg L-1) produces the best absolute feed conversion ratio and weight growth 2.61 ± 0.34 and 0.29 ± 0.04 g and is significantly different from treatment K (0 mg L-1).
Keyword: Bacteria, Bioremediation, Cyprinus rubrofuscus, Nitrification, Bakteri, Bioremediasi, Cyprinus rubrofuscus, Nitrifikasi

Judul: Isolation and Selection of Bacillus sp. as the Microbial Agent for Ammonia, Nitrite and Nitrate Degradation in Catfish dan Goldfish Rearing Environment.
Abstrak: Intensive fish farming which applying high stocking densities requires a high amount of feed input. This will result in accumulation of organic and inorganic materials (including ammonia, nitrite and nitrate compounds) which are toxic to fish. Those problems can be resolve by the application of probiotics which have the ability for bioremediation as Bacillus sp. The spores of Bacillus sp. have advantages because it is more stable for a long time. The use of probiotic Bacillus sp. involved in nitrification and denitrification processes in aerobic condition will reduce the accumulation of ammonia, nitrite and nitrate in the fish rearing environment, since the compounds will be converted into nitrogen gas. This study aimed to isolate and select Bacillus sp. species as a potential microbial agent which will degradate the toxic metabolites such as ammonia, nitrite and nitrate These research have four stages : (1) the isolation of Bacillus sp. from water, waterplant’s root and sediment in freshwater fish ponds,(2) the selection of bacteria in basal media for nitrification and denitrification,(3) the selection of bacteria in synthetic pond water medium and (4) the selection of Bacillus sp. ability in the in vivo test (. in catfish and goldfish rearing environment). Among collection of our isolates, Bacillus cereus and Bacillus subtilis showed the highest ammonia degradation; as much as 56,60% and 63,18% respectively from the initial concentration of 131 mg/l TAN (Total Ammonia Nitrogen); and nitrate compound as much as 40,97% and 26,51% respectively from the initial concentration 530 mg/l. The mixed of two isolates designated by Bacillus cereus and Bacillus subtilis in synthetic pond water showed the highest capability in oxidizing ammonia (66,32%) from the initial concentration of 30,2 mg/l TAN and the reduction of nitrite (19,77%) from the initial concentration of 0,263 mg/l nitrite and nitrate (28,37%) compounds from the initial concentration of 32,6 mg/l nitrate. In the in vivo experiment, using carp and catfish (4-5 cm) in the aquaria (30 l). Each fish exposed in the control water (without inoculation of bacteria) and treatment water (with a mixture of Bacillus cereus and Bacillus subtilis inoculation, 109 cfu/ml total isolate, 3 ml/aquaria). In the in vivo experiments, TAN and nitrate concentrations in treatments inoculated by isolates were lower compared to that of control (without any isolate inoculation) (statistical tests P <0.05), whereas the nitrite concentration in the control and treatment were not significantly different. The inoculation of Bacillus cereus and Bacillus subtilis Keywords: Bacillus sp., ammonia degradation, degradation of nitrite, nitrate reduction showed ammonia degradation as much as 30% from the initial concentration of 6,12 mg/l TAN, and reduce carp and catfish’s mortality compared to that of control.
Keyword: Bacillus sp, ammonia degradation, degradation of nitrite, nitrate reduction

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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