P-You smart bleep! I would say something really smart but have to calm down a bit because of the RC police!
No, don't have any of the Vortechs because in my system, the price of a single mp10 outweighed the benefits in my last system. I couldn't see spending the amount of chedda on a WAVEMAKER (ha ha) versus the benefits it was going to provide. In my next system, you bet your sweet behind I will.
but here is the math and the golden rule to water turn over in a system. Everything that i have read and research in this hobby is that the rule in a closed loop system (your display tank) is that the water must be turned over 10x in one hour, minimum. There is also a thing called to much flow in which corals do not get the nutrients they need to grow and thrive because they can't absorb them: to much flow. Very similar to light--there is a balance between to much and to little. So here is the lesson for tonight.
Since we are using Sal's system we will use this as our standard. 10 x 90 gallons (size of Sal's system)=900 gallons per hour that the water must be turned over inside the system in order for it to thrive. Ok lets round that number up to 1000 GPH. A single Vortech MP10 from Ectoech from the spec sheets state that one single pump can turn over 200-1575 GPH. So lets say we drive that up to its full potential, 1575 GPH. One single MP10 theoretically can turn over the water in Sal's display tank. He needs at least minimum a pump that can do 1000 GPH. So if he were to get at least one MP10, that would be more then sufficient: 1575 - 1000=575. But if he gets 2 MP10, that would equate to 1575 x 2=3150 GPH the 2 pumps are turning the water over: 3150-1000=2150 GPH extra the pumps are pushing. Not bad and more then enough.
2 MP40's as stated provides flow of 1000-3200 GPH. Lets say he does gets 2 and throttles them down to 50% capacity. That would equate to 2250 (1000-3200=2200/2=1100+1000=2250) GPH x 2=4500 GPH. But why would you purchase 2 MP40's and use them at half of their capabilities while spending more money? When you can buy 2 MP10's for the price of one MP40 and use them to their full capabilities. The math does not refute that 2 MP10's are more then capable of keeping this system thriving. Again, i am only taking the specs of the pumps from the mfg and the gallon/hour turn over rate in this hobby, 10x.
So in conclusion, these are hands down the best pumps in the market. Are they being used the right way? Hey, to each their own. However, to say that Sal needs 2 MP40's in a 90 gallon system is to much flow. And using them at 1/2 of their capabilities while spending more does not justify it: cost out weighing the benefits gentle flow or not as advertised. Furthermore, the datum provided justifies that 2 MP10's are more then adequate to maintain a healthy reef in a closed loop system. Here, the cost and benefit of having MP10's are justifiable.
Thank you. This concludes the lesson for today.
I should be a teacher or professor
Yes one MP40 in my 90 but I also had a closed loop powered by a Pan World 50PX-X (1110 gph). So I would recommend two MP40's for the 90 also. 
