there have been plenty of threads that will answer your questions, just check out the advanced search section and type in yo8ur question there. i am not sure about the ebb and flow otherwise id answer myself. I run the ebb and grow and flood 3 times a day during the light hours. 5.8 is perfect, but 5.5-6.3 is acceptable. Generally it will rise over time and you may have to knock it down with some ph down. Im running the lucas forumla and never have to ph it, the nutrients make the water a perfect 5.8ish and stays stable with regular top offs. Ph is important, if your new, make it a habbit of keeping a very close eye on the ph, dont get lazy. Many beginner problems stem from unstable ph, commonly mistaken for nutrient defficincies.