SPS and flow

[chef]

When I was diving in Bali and gili, I couldn't believe how strong the current was. In shallow water (with beautiful colorful sps) I was getting tossed around and thinking I could never duplicate this in an indoor reef. The water however was moving in many different directions as opposed to being "blown" by a powehead.

[Myka]

In my experience, you can have lower flow with frags (like 30-50x turnover), but if there is a point where the corals are impeding the flow then you need big flow just to keep the water column moving. It depends a lot more on aquascaping and coral growth than anything. If there are tons of corals and little swimming space it makes sense you need bigger pumps to make it across the tank, right? Some tanks are aquascaped with a ton of water space even with big coral growth, and these tanks require less flow. My old 90 had around 50-60x turnover when the corals were smaller, I bumped it up around 100x turnover when the corals were in the 10"+ range and the difference was like night and day in color and polyp extension. I am a believer that flow is at least as important as light to SPS corals. If you have good flow you can slack in the lighting department.

[Aquattro]

I agree that as things grow, flow may need to be increased, depending on the variables you mention. I can't offer an opinion on importance in relation to lighting, as I've always had tons of both in any of my tanks.
This is new territory, and I'll adjust as needed, but starting slower just to appease the fish

[sumpfinfishe]

Funny you post this Brad as I have had the exact same concern lately.
My tank has been up for a year now and i have been running two mp10's at 80% in reef crest mode for the last 6 months. The growth of my sps frags has been moderate to high but mostly encrusting and not in height. Lately i have read a few post on various forums that some reefers have been adjusting from this mode to lagoon mode and dropping there pumps back to 50% with no ill effects and some are stating better growth results in just a few short months.
So last week i changed to lagoon mode and also lowered both my mp10's to 50%, in the short 6 days i have not witnessed any negative effects to polyp expansion and the fish seem to be more active as well.
Time will tell I guess

[Aquattro]

Rich, yes, with stronger flow I find they encrust more, and grow in girth before height to build strength to withstand the force of the water. Without this force, they tend to grow up more, but thinner and less dense skeletal structure.

Perfect example is buying a wild A. humilis colony, with short stubby branches. Once placed in a tank with less than strong flow, the branches taper and grow longer.