knew you'd ask that! by that i mean from a beginners point of view, or more specifically from someone who is new to the hobby and inexperienced (not saying you are, just generalising), you will setup your new tank, all eager and ready to stock it. hopefully you're bound to know that your tank needs cycling as staff at your lfs will have told you that, but thats about as limited as your knowledge goes (typically). so your new tank is setup, all cycling and you are thinking, ok i've been told this takes a while. i can wait. so you wait, your tank has finished cycling, you add fish, you add corals, a week later boom! diatom growth. to some, it "appears to fail". to others, they research, find out this is typically normal so continue. sometime after that you get cyanobacteria growth all over your rocks and substrate, again, to some it "appears to fail" not realising that this is reasonably common. however if you dont have knowledge, you start questioning the method of filtration you're using, you question the hardware the lfs sold you. but you continue again, green algae, more diatoms, bad algae everywhere. does the beginner think they are failing? do they give up? do they think the filtration they're using is adequate? only if they believe what appears to be failure is in fact common for anyone setting up a tank. you've just got to battle through it! get my meaning now?!