I hear sand is the best for oscars i dunno why tho, my choice is gravel because of the simple fact sand is way to hard to clean, i have sand with one oscar and gravel with my other oscar and i hate the fact that i changed to sand. With the large rocks make sure there large enough so they dont move them, my 10+" oscar moves rocks against the glass that bad that i fear he might crack the tank, im about to get them out after i write this anyway.
