<![CDATA[ABSTRACT: The present study aimed to determine the effect of different pH level on the density of Skeletonema costatum. A completely randomized design (CRD) consisting of four treatments with 4 replications, including pH 5, pH 6, pH 7 (Control), and pH 8 was applied. Skeletonema costatum density rate and water quality were measured for data collection. A One-Way ANOVA was performed for statiscal analysis and analyzed descriptively. The results showed that the highest Skeletonema costatum density was obtained at pH 8 (26,667 cells/ml), then pH 7 (13,333 cells/ml), pH 6 (11,000 cells/ml) and the lowest Skeletonema costatum density was found at pH 5 (10,000 cells/ml). Statistically, the pH had a significant effect on the density of Skeletonema costatum (p <0.05). this finding suggests that the optimal pH level for rearing was pH 8. ABSTRAK: Penelitian ini bertujuan untuk mengetahui pengaruh perbedaan pH terhadap kepadatan fitoplankton Skeletonema costatum. Metode yang digunakan Rancangan Acak Lengkap (RAL) yang terdiri dari empat perlakuan yaitu pH 5, pH 6, pH 7 (Kontrol), dan pH 8. Tiap perlakuan dilakukan tiga kali pengulangan sehingga diperoleh 12 unit percobaan. Parameter yang di uji meliputi laju Kepadatan Skeletonema costatum dan kualitas air. Analisis data menggunakan one way ANOVA untuk melihat signifikasi pengaruh perlakuan terhadap Kepadatan Skeletonema costatum dan hasil uji Kepadatan Skeletonema costatum di analisis secara deskriptif. Hasil penelitian ini memunjukkan kepadatan Skeletonema costatum tertinggi diperoleh pada pH 8 (26.667 sel/ml), kemudian pH 7 (13.333 sel/ml), pH 6 (11.000 sel/ml) dan Kepadatan Skeletonema costatum terendah pada pH 5 (10.000 sel/ml). Berdasarkan uji Anova, pH memberikan pengaruh nyata terhadap Kepadatan Skeletonema costatum (p<0,05) dengan perlakuan terbaik yakni pH 8.]]>
