The sand bed and rock are going on 3 months, new tank. I didnt think that the PH would swing as much with a refuguim with lights on it. And for flow I have 2 mag 12, so I am guessing a minimum of 1800-2000 gal per hr. I dont think that it is all that heavily stocked as of now, they are all relatively small, 5in body on lion and maybe 12 in eel.