Flow Rates in a reef tank

Hi Guys,



I keep seeing "you need to have a good flow rate" as being the answer to most questions on here but what is considered to be a "good flow rate"?



In my case case I went with basing the math on the circulation rate through the sump ...



circulation = 5 to 10 x total water volume



then I took a look around and see people suggesting that circulation within the display tank should be anything up to 50 x the water volume from posts like this ...



http://ift.tt/1Htgq8L



This seems a bit excessive or am I missing something?



In my case I'm running about 100 gallons / 500L in my setup (total water volume)



So doing the math:

Filtration should be running at roughly 500L x 10 = 5,000 L/hr

And circulation within the tank 500L x 40 = 20,000 L/hr



Is this correct?



If so where do I get flow generators that can push that kind of flow rate round my tank?



My current filtration pump is doing about 5,000 L/hr when accounting for the lift from sump to display but I haven't yet done the math on the circulation pumps, I think it's pretty certain that I don't have enough of them though.



My previous setup was a 55 Gallon (260L) tank with no sump and I had 2 of the 3 circulation pumps I currently use in there as recommended by my LFS as being "powerful enough for 55 gal".



I have a funny feeling though that I'm generating about 10,000 L/hr (each flow gen rated to about 3,200 L/hr) circulation which may be a cause for the excess of cyano i'm trying to battle at the moment (if that rate is not enough).



My thinking is that actually the water volume in the sump probably means nothing for circulation math only filtration (does that sound correct?).



Taking that in to account (if it's correct) I likely need 1 or 2 more circulation pumps to generate flow needed for roughly 75 gallons out of the 90.

Or maybe none at all given that I already added an extra flow pump.



So that raises the question ... if I generate more flow is there such thing as too much flow?