Nothing happens fast, unless you use Dr. Tim's bacteria, then the initial cycle does happen fast (5 days on average). No idea where gangstafish came up with 6-8 weeks to cycle, that is the life cycle of Ich, not the time to cycle a tank. Then again, that picture posted scares the crap out of me, a shark resting on top of a lion? Asking for death. Is that tank size anywhere close to suitable for a shark? Can't tell from the photo, but one thing I can tell, it is a square/rectangle tank which is highly frowned upon for sharks. Sharks and rays should be kept in round tanks, not square tanks. If the shark is in the same tank as the bottom picture, size wise seems big enough for a baby shark, but what happens when it grows up? It doesn't appear to be a 600G+ tank.
Still, I challenge anyone to show me a definition of "cycle". There isn't one. The "initial cycle" is when you have no ammonia or nitrites in the tank but that by no means your tank is fully cycled, a fully cycled tank can take many years depending on your definition.
As for flow/turnover, I would actually say 20x should be the bottom limit for saltwater display tanks (tanks with rock in it). 10x for QT tanks because there are no obstructions like rock to break up/slow down flow.