I have had MANY tanks set up since beginning the hobby. In the beginning, I'd stack rock any which way I liked. I ALWAYS had circulation problems. I now keep my rock off of the sand, by way of
PVC stands, and at least 1 inch away from any glass. Not only does it promote better circulation, but it helps when cleaning the glass of algae. I'd agree here that your
LFS gave GOOD advice.
The Nano Streams are EACH pumping about 1,190
GPH. In a 120, this is about a 20X turnover rate of internal flow. You mentioned the 4 return nozzles, but didn't tell us what kind of pump is returning said flow. You would want to include the "gallons per hour" of that pump, minus any head loss, in your equation.
Personally, I think you'd have some problems with flow that is too low. Granted, you aren't into SPS yet (which LOVE high flow), but even with LPS, softies etc. you would probably have a problem with
detritus settling, and causing algae blooms or water problems. I have a 50X turnover in my little 38 gallon system. Some folks have gone into the hundred + of gallons per hour in flow rate.
What is more important, is area coverage (this is what Mr.
LFS meant by "dead zones"). If you have this 20X turnover rate, and the pumps are moving water in the MAJORITY of area in your system, you COULD be okay. If, however, you have a lot of
live rock in there, and the power heads and/or return nozzles don't provide adequate coverage, you will have dead spots in flow, and therefore, sessile inverts in that area(s) will suffer. You will also find that this is where all the
detritus will pile up. Remember, the goal of flow is to rid the sessile inverts of waste, since they depend on the water to do so. Another goal is to keep the
detritus and other impurities in the water column, so it can be taken into the
sump,
skimmer etc. to be removed.
When using the controller, you really want to ensure that the "switching" doesn't happen fast. You want the pumps to push as much water to reach the capable "fetch". What I mean is, if you have a pump that pushes 1,190
GPH, but it switches off after three seconds, you didn't give the pump enough time to "stream" as far as it could. Therefore, you are going to have dead flow in areas where the water stream stopped before the pump reached it's full capability.
One of the benefits of using products like B-Ionics and other supplements that "cloud" water for a short time, is that when you introduce it to the system, you can track the flow of water. If I add any supplements like this, I watch the flow pattern, marked by the chalky white water. IF I see areas that don't get the "white wave", I adjust pumps accordingly. This is just a tip for users of said products. I'D NOT add it for this experiment, unless you need it.
Dave
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