Two field experiments were conducted at the Experimental Farm of Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt, during 2009and 2010 summer seasons to investigate the effect of irrigation intervals,3-days "T1",6-days "T2" and 9-days "T3" on three rice cultivars; namely, Giza 177, "V1", Giza 178 "V2" and Sakha 104 "V3" with Algalization (cyanobacteria) rates; namely, control (without Algalization, C0), 1000 g/fed "C1" and 1500 g/fed "C2 ". The data showed that Giza 178 gave the highest values, while, Giza 177 had the lowest for plant height, number of tillers/m² and   number of roots/hill.   Also,  Giza 177 had  the  superiority over  the  other  two cultivars   in  grain  yield  and   water  utilization.  This efficiency   could  be attributed to its higher number of filled grains/panicle, sterility( %) and 1000- grain weight.  On the other side, the gel consistency and gelatinization temperature of all rice cultivars were soft and low, respectively.   Data clarified that increasing   irrigation   intervals decreased   plant   height,   number of ,    tillers/m2 DMA, panicles length, number of panicles/ m², number of filled  gains/panicle, 1000-grain weight and grain yield. However, the opposite was true for sterility percentage and WUE.  In addition, rice quality was not significantly affected by irrigation intervals. All growth characters were significantly increased due to Algalization compared to the non-algalized plots. Also, grain yield, grain yield components, WUE and rice quality were significantly increased due to algalization, compared to the non-algalized plots. Generally, it could be concluded that, from the study, rice might be  irrigated every six days and save water without deleterious effects, on its  production,  under Algalization  with cyanobacteria  with  the  rate ranged from 1000 to 1500 g/fed.