What are your thoughts on a vortex commonly refered as a Whirlpool

I wanted to break this out of another thread and open it up for discussion.
I will post a few questions to start this thread.

What is the best way to provide the maximum flow with the least energy?
Are there dead areas in the corners of a square tank using a vortex?
Which is better to move water, random flow or vortex.

I will post later as I am a little busy at work.
Rules for Debate:
Give your opinion but be ready for opinions that counters your own.
Try not to embed quotes as far too ofter they are taken as a direct assault on the person vs. an opinion. Instead use the persons name and be polite. Since none of us have a PhD in water dynamics there is no authoritative answer.

I think there are a few things to consider.

First is the principle of a vortex:
Like a centrifuge objects towards the center will spin faster then the objects along the edges. With this premise in mind we can look at how this will come in to play when considering water in a rectangular tank. With the surface water spinning in a vortex, as you get deeper in the water column the water will spin faster and tighter. This tightening of the water column would prevent the outer edges of water from spinning, thus becoming dead spots in the tank.

Secondly would be the type of flow our animals prefer:
Now not being any type of “Fish Whisperer” or “Coral Talker” I can only go off the basis of what I have previously read in that our animals prefer random, chaotic flow such as that found in the ocean from waves and currents. This is the basic premise of us trying to replicate nature as closely as possible within our marine environments.

So I would have to assume based on this opinion that our animals, specifically the coral, would not be nearly as happy and healthy in an environment where the water spins in the same direction, at the same speed all day everyday. I would even venture to say that a consistent pattern of this nature would have a noticeable and distinct effect on the growth and overall shape of the corals we keep.

Hey rules! I’m sure everyone will still argue thou :wink:

My 2cents, I’d venture to think that a vortex would move more water than standard/random flow and reduce dead spots. BUT I believe it would cause more laminar flow and not turbulent flow. Most corals and creatures prefer the wish wash (wave) flow and more turbulent flow to disrupt algae on them and bring away waste, or so I’ve read.

Now if you had two seperate vortex setups (Setup 1: back left front right, and Setup 2:back right front left) that ran like a wave maker then you’d have the best of both worlds.

Remember I don’t have as much experience as everyone else, so take my thoughts with a grain of salt!

Note: posted the same time as Craig :wink:

OK I am new at this so I can’t really say what the animals would like better but I would guess random.

Anyway so it has been over 10 years since I had my fluid dynamics class, but I have worked on some pipe fluid flow stuff since then. Please feel free to correct me if I am wrong on any of these principles (just be warned I may break out the textbooks when I go back to work on Monday >LOL<) Whenever you have laminar flow the fluid that touches the pipe wall does not move and the flow in the center is moving quicker than the fluid closer to the wall (this makes it easier for the algae to grow in the return tube that people have mentioned). So I am not sure how you would not have dead spots around the edges of the tank and especially in the corners. Remember everything in nature travels the path of least resistance.

Also anything in your tank – rock (live or otherwise), coral, lets ignore what effect the fish have on the flow – will cause eddies on the downstream side of the flow. Think of video you may have seen of windtunnel tests with the smoke. So the downstream side of the rock, coral, etc will also have dead spots.

As for the energy, depends if you are talking about center of tank, edges of tank, or overall. Man its the weekend I should have to think about stuff like this. verdict_in


Ok, her is my attemp to comment on this topic. I don’t have a PhD, but working on my GED as we speak >LOL<. Vortex even thou provided the max flow, it is less effective than random flow IMHO. How do I come to that conclusion you may ask? Take a bit of sand, put it into a water bottle and swirl it around really fast in a clockwise or counter-clockwise motion until you create a vortex and see where the sand end up. IN THE MIDDLE. But if you do the same thing forward-to-back and side-to-side, you will have a better mix even if you doing it more slowly. Does it make sense to anyone or is it just made sense to me?

[quote=“Adictedtoswf, post:5, topic:1072”]
Ok, her is my attemp to comment on this topic. I don’t have a PhD, but working on my GED as we speak >LOL<. Vortex even thou provided the max flow, it is less effective than random flow IMHO. How do I come to that conclusion you may ask? Take a bit of sand, put it into a water bottle and swirl it around really fast in a clockwise or counter-clockwise motion until you create a vortex and see where the sand end up. IN THE MIDDLE. But if you do the same thing forward-to-back and side-to-side, you will have a better mix even if you doing it more slowly. Does it make sense to anyone or is it just made sense to me?[/quote]

Good point…

I think that would then be more efficient but not as random as to where the grain of sand will end up.

I wanted to start by saying a vortex will not work as efficiently in every tank style nor will it provide a specific coral a large increase in flow. It will move a large body of water using less energy then any other method. I am not suggesting that a power head will not be needed to give extra flow to a specific coral just that instead of trying to create small pockets of turbulent flow it would be more efficient to created a vortex and supplement with a powerhead.


Little facts provided by Wiki http://www.wikipedia.org/
A whirlpool is a swirling body of water usually produced by ocean tides. The vast majority of whirlpools are not very powerful. More powerful ones are more properly termed maelstroms. Vortex is the proper term for any whirlpool that has a downdraft

A vortex is a spinning, often turbulent, flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex. The speed and rate of rotation of the fluid are greatest at the center, and decrease progressively with distance from the center.

A gyre is any manner of swirling vortex, particularly large-scale wind and ocean currents.

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms (and for liquids only), viscosity is “thickness”. Thus, water is “thin”, having a lower viscosity,


This question of using a vortex or gyre is not new just not mainstream in an aquarium. This being said I am not spearheading a change that’s radical but showing an option that is lost in the verbiage of Laminar Flow. The vortex created in a large scale whirlpool is impressive enough to sink ships. Two years ago I was mentioning to Kaptken of wanting to reduce the amount of money I spend running my tank and we hit the usual suspects; lights, heaters and pumps. I had a few Ideas how to reduce my lights electric consumption and I was going to insulate select areas of the tank to hold heat in the winter. (Tank was in the basement and used the heater a lot) However, I was still lacking a way of reducing the cost of the pumps providing flow when Ken recalled a conversation with a vendor about whirlpools.

Whirlpools are created and grow based on the physical attraction on water to its self. Combine this attraction with its low viscosity and a small force can move a mountain of water. There is no more efficient use of energy to return in water movement available to the aquariest. In nature the ocean is a series of gyres. Wind Driven Surface Currents: Gyres Background
In fact the entire ocean and winds are all forms of gyre. Its truly efficient and where we will be using a small pump to effectively create a vortex, the ones in nature are powered by wind, convection tides, currents, the moon and the earth rotation. (among others)

Example A:
Remember as a kid being in a small above ground pool and yourself or your kids would move around the outside of the pool as fast as you could? As soon as the vortex was strong you would try to stop. You got dragged along didn’t you?

Example B:

Notice as the water gives in to gravity it stretches till finally the bond of the water is overcome by gravity. This works because a water molecule having a positive charge on the side where the hydrogen atoms are and a negative charge on the other side, where the oxygen atom is cause the molecules to attract.

All these water molecules attracting each other mean they tend to clump together. This is why water drops are, in fact, drops! If it wasn’t for some of Earth’s forces, such as gravity, a drop of water would be ball shaped. This is also why a laminar flow is so effective in moving water with less power. Conversely two flow directed into each other to create a chaotic turbulent flow has to overcome this attraction of molecules along with the friction created by water passing over water.

Example C:
i wish we could embed video as this is a cool vortex and at various speeds you see the turbulence that is created on the glass walls as water swirls around the semi square container. This is in line to what we are trying to replicate. Not a tight center eye but a large eye that washes the face of the rock work to bathe corals with food and remove waste.


Water that is in the corners of a square tank may not flow as fast as it will in the center but the corner will have no less flow in any tank using a directional powerhead with water crashing into the output of another. They both will encounter a buffer zone in the corners. The water in a vortex is traveling at the same speed inside and out but since the water is traveling a shorter distance in the center it appears faster.
To get the dynamic flow in the corner you could aim a powerhead directly into the corner but how many corals make it to the corner and need the flow?
Overall because of the tension of water molecules wanting to hold together they will pull water out of the corner albeit slower then at the center of the vortex. won’t the water that contacts the corner create a chaotic flow area as it crashes into the corner?

Since water in a vortex tend to collect debris at the center in an specific area it allows for easy removal during water changes. To reuse an example used earlier that “sand” will move all around the bottom of the tank in turbulent flow, so will the debris leaving it scattered around the tank.

Science and published marine biologist are a funny thing; rarely will one publish something that will get the author ouster sized and ruin a payday. While some may hint at a new direction it is a painstaking ordeal for it to mainstream. Jocephus mentioned that not everything in nature follows the book and while its great to be versed you have to experience it first hand.

Using the turbulent flow method does creates a random flow that our animals get in nature. While this represent what we may find in nature it is not the exclusive realm that a coral will live or flourish. Is it as chaotic and random on the inside of a reef as it is at the top or outside edge? There are tidal pools that sustain reefs where during low tide some corals are out of the water or in stagnate water for hours. While it is our intent to replicate nature as closely as possible it does not mean there are not more efficient ways to provide the needed flow that corals rely on to remove waste and bring dinner.

There have been some studies that flow may effect the growth of a coral. But what happens when water flowing laminar crosses an object? Turbulence is created. Every rock and coral will add a degree of turbulence. Turbulence is quite beneficial for diffusion and mixing as it helps corals breathe and expel waste. However, it is very inefficient in terms of overall bulk motion. Laminar flow stores and best conserves kinetic energy in the flow. This is why a small pump placed correctly can cause a whirlpool of flow after a few minutes of constructive flow acceleration.

It takes more equipment and energy to provide true chaotic and turbulent flow that mimics true nature then the benefits of a low energy vortex. Corals need some turbulence to remove debris and provide nutrients. Most of the flow created by raming two powerheads output together is lost in a short distance. You can create the most overall flow by creating a vortex and the turbulence will be created as the laminar flow runs into objects.

Great reads if you have some time
Measuring Turbulent Flow In Reef Tanks
Water Flow is More Important for Corals Than Light, Part V

This applied somewhat and just looked real cool

properties of magnetic vortices


I recall, a profound speaker and experimenter at the 2007 NJRC frag swap discussed just this point. His experiments and calculations agree that a couple power heads placed in opposite corners of the tank, near the surface, blowing in the same direction gave the max rotational water movement over time. and if you placed them for counter clockwise rotation, you get the boost from the coreolis effect ofthe earth rotation and gravity. something to do with the right hand rule of torque rotation, i think. which is why all toilets flush counter clockwise to take advantage of the force.

as Al posted, rock and coral in the tank drag down rotation. so the clear layer of water near the surface is easiest to set in motion, and through friction of layers of water will movethe lower tank water too. smooth flow of adequate velocity is essential for coral respiration and chemical exchange and absorption from and with the water.

Toilets in Australia flush the other direction.

Gee - does anyone else think it’s fishy that Al seemed to have all of this information readily available?? Why is it always the guy that starts the debate topic that seems to have the most ammunition???

Forgot to add:

verdict_in YahoO :SPIT) >LOL<

PoM Al!!!


Aw come on…Who is going to take the topic further? I did learn something reading this; I never knew toilets flushed one direction to take advantage of the earths rotation. It made sense but of course I tested it. This would also mean setting up a vortex in your tank that is located in the northern hemisphere would also be more efficient going counter clockwise.

Well Al I took our experiment one step further and began testing the vortex in all of my sinks. For those that weren’t on the phone call, we were curious as to whether a toilet in the northern hemisphere flushed counter-clockwise as a result of the earths gravitational pull or because that’s how Jethro in the toilet factory pointed the water nozzles in the bowl.

we decided to look at how water drains naturally with no assistance or persuasion from directional measures or apparatus.

The powder room on the first floor drains counter-clockwise. However the sink in the main bath upstairs drains clock-wise. The tub - with no external stopper also drains counter clockwise.
Now I am curious to know if the distance between the flange on a drain stopper and the porcelain of the sink will provide enough friction to alter the natural tendency of water to flow in a counter-clockwise direction as it moves towards the southern hemisphere.

yup, the effect is the opposite direction in the southern hemisphere.

Yous guys are pretty sharp.

But placing your power heads high in the tank , in the same direction gets the most water movement. about 3-5 CM/sec i think. just a nice smooth flow it improve coral respiration and exchange. In a fuge it makes plants grow better too. That was one of Sarah’s sea grass experiments i believe.

[quote=“kaptken, post:16, topic:1072”]
…placing your power heads high in the tank …[/quote]

Why is that Ken? Less things up high to impede flow? Surface of the water impedes flow less than water on top?

Craig, how level are your sinks?

What does everyone think about the conflicting vortex idea I posted earlier?

friction of laminar layers of water gets the whole tank spinning. like stacking a bunch of slippery CDs on spindle, and start spinning the top one. in time you get the bottom one spinning too. not as fast as the top, frictional loss. but it will be moving.

Ian, having the pump up high reduces the amount of water it has to move before the vortex starts. Once started it will carry through the water column and the entire tank will move. It should not be breaking the surface.

[quote=“IanH, post:3, topic:1072”]
Now if you had two seperate vortex setups (Setup 1: back left front right, and Setup 2:back right front left) that ran like a wave maker then you’d have the best of both worlds.[/quote]
Is this the idea?
I would think creating a small vortex in 2 separate areas of the tank will be impossible with out a barrier to start the swirl.
I thought of another idea that I was going to attempt to create some chaos in the water column. Have one pump going one direction and a couple hours later it would shut off as another pump facing the reverse direction start. Almost tidal and would reduce any coral growth issues often associated to laminar flow. (may or not be true)