If you can eliminate dead-zones and detritus from collecting all throught your sandbed and LR while only having 10x-15x turnover in your tank, go for it. If you can distribute 10x-15x turnover throught the entire system in a manner that will provide proper flow to all corals, go for it. You will notice MUCH better growth, polyp extension, "plumpness" of tissue, extension of feeding tentacles, longer skirtes in zoantids and palys, etc with a more appropriate flow closer to 30x-40x per hour. You will also notice that you will not have to clean your sandbed, you will not get any detritus build-up around the base of your LR, you will not have any dead-spots, and you will keep "solids" in suspension where it can be properly removed by your filtration.
There are MANY MANY variables to consider too. What kind of flow do you have, your rockwork, denisty of corals, what kind of corals, etc. I can guarantee you though that you WILL NOT see the same results in a 20g (for example) that has 200GPH as opposed to 400-600GPH. And really, you almost HAVE TO TRY to keep yourself limited to 10-15x turnover. If you have a HOB powerfilter and a powerhead or two that are appropriatly sized for a 20g tank, you are already looking at about 500 gph.
Also consider where most of our corals are located... shallow tropical reefs at around 5ft-30ft of depth. This is the most turbulant part of the entire ocean! Constant tidal fluctuations, waves, storms, etc. If you had 100x turnover in a tank, that is NOWHERE NEAR what the corals would experience on their home reef.
And the topic of 100% water changes is A WHOLE DIFFERENT THREAD. But if you are trying to say that someone who practices everything he preaches, tours the country and the world teaching and speaking, studies reef tanks and HUSBANDRY FOR A LIVING, and has threads that are dedicated for him to answer people's questions on multiple sites is someone whos info cannot be trusted, your crazy. Calfo does weekly 99%-100% water changes and has showed tremendous pictoral evidence of the benefits. Edgray (a member of this site) also practices this method and he too has shown incredible results. BTW, he also has like 3 powerheads in his 12g including an upgraded return pump.
You also misunderstand MY system. I do have alternating current, yes. It alternates every 6 seconds. BUT, it alternates 650gph ... this means that 650 gph comes from one end of the tank... then that 650 gph alternates to the other end of the tank.
You also wouldnt need 7.5 powerheads in your tank if you had the appropriatly sized powerheads. MJ600's are good to eliminate dead zones behind your LR or around the sandbed, but they are designed for smaller tanks. If you had 3 MJ1200s, you would be right around 900 gph and be at about 30x turnover... a much better place to be.
What you have to remember is that corals are sessile inverts that really entirely on water flow for removing the wastes they create as well as the noxious chemicals that they create (which can lead do RTN, loss of growth, and death), and also for food supply. many corals get some of their nutrients from the water column.
It is an indisputable fact that there are three EQUALLY IMPORTANT factors in a reef tank... 1), proper lighting 2)proper water quality 3) proper water flow.
Jesse
oh yea and there are zoas in there too and they love it too