What am I trying to achieve with Flow?

[Tom Toro]

I've gone Tunze/flow happy in both of my tanks. The 135sps has a closed loop/Dart and 4 6100 tunzes on a controller. I just bought another 4 and controller for the 240 anemone/fish/softies. With sand in both of them now, the sand is blowing all over the place and creating dunes no matter where I shoot the flow (135). I've got the 4 in the 135 turned down to 30%. Haven't hooked up the 4 in the 240 yet, but with just the hammerhead return pump, I'm getting movement on all of my corals/anemones.

Q:What am I trying to achieve in both of these setups regarding flow? When do you know when you have enough/too much/not enough? Is a wave the ultimate flow or random or what? Sps are supposed to have tons of flow, I've been told. Why?

[dlhirst]

The right amount of flow will keep detritus from settling to the bottom of your tank where it tends to become food for algae. By holding it in the water column, it can both feed some of your corals and also be swept towards your skimmer for ultimate removal.
SPS tend to be found in tidal regions where wave action makes for high water movement.

[binford4000]

YUP you have monster flow !!! That's allot of gph your pushing there.Flows very important but it's easy to get carried away.That's right I actually said that. I also have a closed loop and had the multiple tunze's going as you do.To the point I had to epoxy stuff down or it was going surfing.I read Anthony Calfo's book and it really changed my opinon and what I thought I new from reading fourms and talking to any fish geek I could listen too.If your only running at 30 % you should reavaluate what your flow plan is.I ditched the tunzes(actually gave them away) and went for a wider less aggressive flow(vortech mp 40) I know look for detrius suspension and dead spots.As long as the water is passing over the corals they are getting fed and absobing nutrients. I tested my tank for flow with a kent target feeder and watched what the phyto plankton was doing.If it satyed in place I adjusted accordingly tell I got movement in all the places I tested. I was able to replace 2 korilla 4's and 4- 6125 uni balls with just two Mp40's and a MP10 that creates bottom flow accross the sand bed,with the wireless controlers I have more flow options then ever.I am now even considering unplugging the closed loop,seems like a waste of money.I noticed considerable polyp extension and have enjoyed better growth since getting off the sunami wagon.You should see how fuzzy the pink birdsnest you gave me is !!Just my .02 tho Tom. Maybee you should try one tunze on each end see if you notice a change with a concentration on dead spots.I would be intrested if you get the same results.Good luck