The purpose of this study was to determine the effect of using fermented red seaweed (Euchema cottonii) waste flour in the ration on the consumption and digestibility of calcium and phosphorus in the grower phase of landrace crossbreed pigs. 12 pigs aged 3-5 months with an average initial body weight of 49.1kg, with a coefficient of variance of 25.52%. The design used in this study was a RAK consisting of 4 treatments and 3 replications. The treatments tested is R0: 100% basal ration without fermented seaweed waste flour (control), R1: 95% basal ration + 5% fermented seaweed waste flour, R2: 90% basal ration + 10% fermented seaweed waste flour, R3: 85% basal ration + 15% fermented seaweed waste flour. The variables measured were the consumption and digestibility of calcium and phosporous. ANOVA result show that the treatment had no significant effect (P>0.05) on the consumption of P, and the digestibility of Ca and P, but the consumption of Ca had a significant effect (P <0.05). The results of further tests on Ca consumption showed that treatment R3 had a significant effect (P<0.05) on R0 but had no significant effect (P>0.05) on R1 and R2, treatment R2 had a significant effect (P<0.05) on R0 but did not have a significant effect (P>0.05) on R1, the treatment of R1 had no significant effect (P>0.05) on R0. The conclusion of this study is that the use of fermented seaweed waste flour in rations up to a level of 15% has not been able to affect the increase in P consumption and the digestibility of Ca and P, but at the level of 10-15% it can have an effect on calcium consumption in pigs.   Tujuan penelitian untuk mengetahui pengaruh penggunaan tepung limbah rumput laut merah (Euchema cottonii) terfermentasi dalam ransum terhadap konsumsi dan kecernaan kalsium dan fosfor babi peranakan landrace fase grower. Ternak babi sebanyak 12 ekor berumur 3-5 bulan, rataan berat badan awal 49,1kg, dengan koefisien varians 25,523%. Rancangan yang digunakan yakni RAK terdiri dari 4 perlakuan dan 3 ulangan. Perlakuan yang diuji yakmi R0: 100% ransum basal tanpa tepung limbah rumput laut terfermentasi (control), R1: 95% ransum basal + 5% tepung limbah rumput laut terfermentasi, R2: 90% ransum basal + 10% tepung limbah rumput laut terfementasi, R3: 85% ransum basal + 15% tepung limbah rumput laut terfermentasi. Variabel yang diukur adalah konsumsi dan kecernaan kalsium dan fosfor. Hasil ANOVA menunjukan perlakuan berpengaruh tidak nyata (P>0,05) terhadap konsumsi P, dan kecernaan Ca dan P, akan tetapi konsumsi Ca berpengaruh nyata (P<0,05). Hasil uji  lanjut terhadap komsumsi Ca menunjukan bahwa perlakuan R3 berpengaruh nyata (P<0,05) terhadap R0 tetapi tidak berpengaruh nyata (P>0,05) terhadap R1 dan R2, perlakuan R2 berpengaruh nyata (P<0,05) terhadap R0 tetapi tidak berpengaruh nyata (P>0,05) terhadap R1, perlakuan R1 berpengaruh tidak nyata (P>0,05) terhadap R0. Kesimpulan penelitian ini adalah bahwa penggunaan tepung limbah  rumput laut terfermentasi dalam ransum hingga level 15% belum mampu memberikan pengaruh terhadap kenaikan konsumsi P dan kecernaan Ca dan P, namun pada level 10-15% mampu memberikan pengaruh terhadap konsumsi kalsium pada ternak babi.