I feel that there is a tendency to overdo things in this hobby, the perfect example in my opinion is light requirements, but flow is no exception. Once the hobby figures out that something is important to the health of the inhabitants, we as a group tend to throw as much at it as possible without really stopping to think why is it important and am I using it in a reasonable manner. Add in the fact that we really don't know what the actual requirements for any one species is, we just tend to overdue it to be "safe"
Yes, SPS needs good flow... does it need to have some obscure quantification measured in total tank turnover approaching the triple digits..absolutely not and I personally think that measuring flow in terms of tank turnover is fairly base. But since it is one of the few quantifications available, we are kind of stuck using it.
This has been touched on in previous posts, but it is more important to have chaotic and changing flow. You want enough flow to keep water moving past your coral, and to prevent detritus from settling on your coral. If your flow does not create a certain amount of randomness in the tank, you will have dead spots where detritus will accumulate, I have found that this is particularly a problem with Monti Caps with the broad plates that seem to want to collect particulate matter. In my 65g tank, I had close to 50X tank volume turnover (there I go bashing a method of measurement and then turning around and using it), and I still found it necessary to blow off my Monti Caps occasionally with a turkey baster which I never did as much as I should. that being said, they thrived.
As to other types of SPS, all I can say is that I noticed that many of my Acros (milli and austera) did not extend their polyps if they had to much flow, and would extend them more if I moved them just a little bit so that they got a much more diffused and (presumably) slower flow. I assumed (for whatever that is worth) that they where "happier". Without attempting the same type of acro under different conditions for a long period and observing their growth, it is hard to say if they really where doing better.
. They are ugly and don't produce good random flow (unless you are willing to spend some $$ for Tunzes).
