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I just read this entire post and it is very fascinating. It might be just me but I find designing a flow pattern to be mostly common sense. Just keep it simple, and it will be effective. Take powerheads for example, I personally feel that there is no place for them in most freshwater tanks, especially planted ones, unless you are running no filter and need it for singular movement.

Think about the natural environment. In a marine environment there is a LOT of turbulence around reefs cause by the water going rapidly from deep to shallow, e.g. waves. With the extremely large volume of a wave there is a lot of pushing and pulling of water in every direction. That's why reefers use so many powerheads pointed in every which direction and wavemakers on top of the outflow from the sump. They are attempting to emulate the corals natural environment on a generally very turbulent reef.

Now look at the typical freshwater plants natural environment. The current almost always flows in a fairly uniform direction, at a uniform speed. Typically there are no harsh cross currents or highly turbulent areas where these plants grow. If you think about a freshwater system, spring to end-point, it seems to me like a giant never ending train, one big continuous cycle. By the way I live in the most lake populous state (stick a sock in it Minnesota) so looking at a map I can see more lakes and river systems than I can count. Anyways what I'm trying to say is typically there is only one directions of water movement, forward. All there is, is where its coming from and where its going. Inflow and outflow. In this context it is easier to imagine the plants natural environment as a closed system and relate it to our own.

What you want, as has been previously mentioned, is one flow, in a loop, with inflow and outflow near the same point. This is as close to a magic formula as you are going to get, unless you want to build the same tank every time, and there is not fun in that. The rest of the details such as direction, flow rate and location are personal to your individual tank and are easily worked out on set up. Just observe and adjust. There are generally plenty of bubbles and other crap floating around in the water, just start with a high flow rate, find your location, find your direction, adjust your flow rate and your done. I feel that this is as close to the natural system as we aquarists can reasonably achieve, and it shouldn't take you 10 minutes. I usually find myself aiming the flow down the largest dimension of open water.

On the subject of laminar vs. turbulent flow, sometimes I find it is hard to have one and not the other. Take my 55 long for example. I was found it was difficult to get uniform flow and total tank coverage due to the length. What I ended up doing was taking the spray nozzle and aiming it directly across the middle of the tank. It was about 3 inch below the surface and blowing parallel to the water line. Once I adjusted the flow rate, it was perfect for my tank! The flow near the surface was of course a pretty turbulent but only a little past half way. When the water hit the other side it slowed a bit and formed a strong undercurrent that when to the bottom and then back across to complete the cycle. And wouldn't you know it, after the turbulence spread out I had perfect, even flow throughout the rest of my tank. The upper-left was turbulent, but the upper-right, bottom-right, and bottom-left were laminar. I also had no dead spots. Like I said though, this was perfect for MY tank. The tallest hardscape was maybe 7 inches and the tallest plants were probably 12, so they were unaffected by the turbulent top few inches, and my dannios loved the turbulent section. They'd sit there a swim head on into the outflow like it was nobodies business.

I love this thread and can't wait to read more on this.
 

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Just wondering, how did you determine that it was turbulent? Did you use food dye or just observe particles in the flow?
When I set the tank up I didn't wash the substrate very thoroughly and there was a lot of particles. (some really dirty gravel I bought at Stein's) Also I had quite a few tetras and some dannios so when I fed them I'd stick a decent sized pinch of flake under water right above the nozzle. The food would hit the blast from the nozzle and I could watch it do 3-4 laps around the aquarium before they would eat all of it. So I've spent a lot of time inspecting the water flow of my tanks. In fact I spend a lot of time in general with my nose up to the glass inspecting one thing or another, some might say too much time Haha.

Crap and I just noticed this.. In my post I used the word "turbulence" a lot, only it wasn't always in a technical sense such as the definition of "turbulent flow", and I never differentiated between the two very well. I hope you catch my drift:biggrin:
 
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