Introduction to Flow, Tank Turnover, and Powerheads for the Reef Tank, Part 3

[R2R Articles]

For inspiration, here is a beautiful 93-gallon cube tank belonging to @vetteguy53081.
View attachment 1014314
Photo is from the Reef2Reef archives, courtesy of @vetteguy53081, ©2019, All Rights Reserved.

And now we come to Part 3, Powerhead Placement.

Everyone is waiting anxiously to hear about powerhead placement; and I hate to disappoint you, but I don't have any magic answers. Everyone's tank has different dimensions and a different aquascape, so it's impossible to make too many generalizations.

Here are the guidelines.

1. Most people don't want to see a lot of equipment on the front viewing glass of the display tank. So, that means that powerheads are generally placed on the sides and on the back of the tank.

2. Since we're trying to avoid laminar flow or flow always in one direction, that means most people put a powerhead on each of two opposite tank sides. And if you don't want pumps in the front, that means you would start with one pump on each side.

3. Most people aim powerheads across the tank or up. Aiming up causes more ripple on the surface which is good for gas exchange but bad for salt creep. Aiming down can cause a sandstorm if you have a sandy substrate. You can also aim powerheads at the wall of the aquarium. You will have to experiment with your own aquarium to see what works for you and your livestock.

4. Similarly, powerheads should be mounted toward the top of the aquarium, but not so close to the water surface that they will be sucking in air instead of water.

5. Then depending on what kinds of powerheads you choose, you can have them flow more or less or off and on to vary the flow.

6. Another possibility is to add one or more powerheads on the back wall that flow more or less or off and on to add to and vary flow patterns. If you have a black rear wall or a rock wall, then you won't see the powerheads.

7. Chaotic flow is good. Surge is great, but the only way to get that is with some kind of surge device. We had a good article about making one a while back written by @garbled.

8. Consider where your overflow is. If you have an overflow, you may want to direct water to circulate such that junk is picked up off the bottom of the tank and flows back towards and up to the overflow.

9. Consider what you plan to house in your tank. If you're aiming for SPS coral, then you may want to get powerheads that are more powerful than you need at the beginning, but that can be dialed down and then up when you need the extra flow.

If you want to watch some videos on this topic, here's one by Bulk Reef Supply:


And another by Current USA on powerhead placement:


Buying a bunch of powerheads isn't cheap, so think about all this carefully before you start buying. However, until your tank is set up and the aquascape is done, it's impossible to know exactly what you will need or how the water will flow.

For inspiration, here is a 10-month-old, 80-gallon mixed reef belonging to @MulletBoy . Notice the Maxspect Gyre on the back wall of the tank.
View attachment 1014338
Photo is from the Reef2Reef archives, courtesy of @MulletBoy ©2019, All Rights Reserved.

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Author Profile: Cynthia White

Cynthia received her BA in English from NYU a long long time ago. She has been a freelance writer and editor for over 20 years. In 2018, she won the President's Award from the Professional Writers Association of Canada. Now she is a writer and editor on staff at R2R, where her forum nickname is @Seawitch.

 

[Hitman]

Awesome write up!

 

[MnFish1]

Another great article

 

[Greg Gdowski]

Nice article Cynthia!

 

[bubblemytip]

This link also has a great video from one of TUNZE’s engineers on pump placement with diagrams etc: https://recifalnews.fr/2017/07/art-of-circulating-with-claude-hug-from-tunze/

 

[MnFish1]

Here is a nice video about the maxspect Gyre.

 

[Seawitch]

This link also has a great video from one of TUNZE’s engineers on pump placement with diagrams etc: https://recifalnews.fr/2017/07/art-of-circulating-with-claude-hug-from-tunze/

This is a great video, and I speak French!

 

[Seawitch]

Here is a nice video about the maxspect Gyre.

This is a really good video, too. Thanks for showing it to me.

 

[w2inc]

Thanks for the write up. I agree that it kind of impossible to know what your water flow is going to look like until the rocks are in the tank. I always want to plan out the perfect system and then just throw it together, but there is a lot of tweaking after the water is in. I agree that there is no right set up and I believe you can make just about any set of pumps work. I have been keeping tanks since about 1979, worked at pet stores and maintenance jobs. Here is where I have landed with my thoughts on pumps.

I like DC pumps because you can control the speed. It is easy to overshoot your flow needs with pumps like they gyre and mp-60 or tunze turbell. I have had generic and brand name pumps fail and work amazingly. I am not recommending a specific one. It is nice to just be able to turn a dial to correct it. I use really large pumps. It is my opinion, but I also think a larger pump running at half speed will wear out slower than as small pump running at full speed. I figure that there is a general number of times the prop can spin around before it dies. Fish get pulled into pumps on occasion. Slower moving higher volume pumps seem to pass them through rather than chop them up. Old school single speed heavy return pumps have their place as well. I use them when I know exactly how much flow I want and have the option to keep them in a separate room where I don't have to listen to them. They have no controller that will break. I use external pumps. They don't get water damage, add heat to your system and just run and run for years putting out really consistent flow.

I hear a lot about random flow, pulse flow and wave surge. I like the tech and just buy it sometimes. It is good to remember that a pump that is surging is only pumping when it is surging and might be off about half the time. So 3000 gph might turn into 1500 (but that might still bet enough).

I do want to say; Is laminar flow really that bad, and can it even really exist in a tank filled with rocks. When I follow the turbulent flow theory it all makes sense, but when I look at a trout stream or fast moving river the theory doesn't really hold up. The river water is all headed on direction but there are all kinds of reverse flow eddies and turbulence. The nutrient sink is way downstream in a lagoon (or on a tank in a filter sock).

I currently have 4 reef tanks from 40, 60, 120 and 140 gallons. They have all kinds of flow but the tank with the single constant speed power head grows the same coral as my tank with the 4 controllable EcoTech Mp wave pumps. Yes, SPS. I prefer massive flow that you can see and not really feel. Meaning that there is not a spot where your hand is getting blasted with water but there is obvious fast water movement. More powerful pumps at full speed can put out a water jet that will damage corals that get in the direct line of fire. I design rock work around them or place them up and away so my animals get indirect flow.

The nozzles that diffuse and randomize flow are cool, but they do cause some head pressure on the pump and it will not push the volume it can without them. I have big power bills and try to be as efficient as possible with my watts per gallon. Oversized plumbing from the sump and eductors after power heads seem to pay out for me. (DIY eductor = power head blowing into a 3 inch pipe hidden under rocks)

I am glad you addressed turnover in a little more depth. Surface agitation allows for excellent gas exchange and lots of that can happen in a sump as well as a tank. I am not sure that what happens in a skimmer could compare to it. I don't know the magic number there but I do think 6x is plenty and might even be fine with 1.5x with the right set up. When keeping specimen tanks like seahorses I use a 12x or higher turnover from the return pump. Power heads can be dangerous for them and the return is normally the only circulation the tank gets. I diffuse the flow by oversizing my return pipes to (about 1.5 inches) with multiple return ports.

For what it is worth, I was given a used Gyre pump and I think they are awesome. Incredible amounts of flow with a little softer focus than the other pumps I own. My experience in the past 3 years has been more reef specific and less fish. Every set up is different and part of the fun is working it out.

Thanks for your article. Great info!

 

[ca1ore]

In terms of laminar flow, we are talking about reefs not freshwater streams or rivers so the comparison is invalid. Freshwater plants are evolved to handle constant, unrelenting laminar flow; marine inverts are not. Certainly on some wild reefs laminar flow may exist for some part of the day, but it usually reverses as the tides change. Various nozzles do enhance water velocity at the expense of overall volume. I don't personally use locline for precisely this reason. The net effect of educators/penductors is less clear. They do sacrifice direct flow but offset that with induced flow.

 

[w2inc]

In terms of laminar flow, we are talking about reefs not freshwater streams or rivers so the comparison is invalid. Freshwater plants are evolved to handle constant, unrelenting laminar flow; marine inverts are not. Certainly on some wild reefs laminar flow may exist for some part of the day, but it usually reverses as the tides change. Various nozzles do enhance water velocity at the expense of overall volume. I don't personally use locline for precisely this reason. The net effect of educators/penductors is less clear. They do sacrifice direct flow but offset that with induced flow.

My comparison was directed toward the behavior of directional water flow of any kind over uneven surfaces relate that flow to nutrient transport. Nothing to do with plant or animal growth. My intent was to demonstrate that any water flowing in the same direction over an uneven surface creates plenty of swirling eddy types of currents. I also hoped to express the possibility that this type of turbulent flow could keep sediment and detritus suspended in a reef tank as it does in a river, until it could land in a filter sock or some other area designed to manage it. It has been my experience that it works.

I may have been off with the definition of laminar flow. For me, it is something like this, "There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids." I do not believe it is possible to have laminar flow in an aquarium that has rock work in it. The rocks cause those eddies and swirls.

My experience with my aquarium that does has flow in only one direction has many of the same corals, (Monti, Digital, bird nest, stag horn, zoa's and mushrooms) as its neighboring tank that has several wave surge pumps. They appear to be equally healthy.

Two months ago I placed seriatopora hystrix, digitata montipora, and montipora capricornis frags in the sump of my 120. It is on the final under flow baffle under about 3 inches of fast moving water. It receives 50 PAR of overflow (pink) light from my Cheato grow section. It breaks all the rules that I was taught. I was looking at them yesterday and they are growing and have good polyp extension. It has lead me to believe that coral frags can adapt and thrive in several environments pretty quickly. I will never claim wave surge is not good for corals. My personal feeling is that there is a little too much marketing directed at it.

I agree about the loc-line. The physics of eductors is pretty well documented. My experience with them is only from experimenting with them observation of flow. I do not have a flow meter to quantify it. I prefer a large smooth high volume flow on my reef. DIY eductors have made this easy for me to achieve. If you have some experience with them I would appreciate more information.

 

[MnFish1]

My comparison was directed toward the behavior of directional water flow of any kind over uneven surfaces relate that flow to nutrient transport. Nothing to do with plant or animal growth. My intent was to demonstrate that any water flowing in the same direction over an uneven surface creates plenty of swirling eddy types of currents. I also hoped to express the possibility that this type of turbulent flow could keep sediment and detritus suspended in a reef tank as it does in a river, until it could land in a filter sock or some other area designed to manage it. It has been my experience that it works.

I may have been off with the definition of laminar flow. For me, it is something like this, "There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids." I do not believe it is possible to have laminar flow in an aquarium that has rock work in it. The rocks cause those eddies and swirls.

My experience with my aquarium that does has flow in only one direction has many of the same corals, (Monti, Digital, bird nest, stag horn, zoa's and mushrooms) as its neighboring tank that has several wave surge pumps. They appear to be equally healthy.

Two months ago I placed seriatopora hystrix, digitata montipora, and montipora capricornis frags in the sump of my 120. It is on the final under flow baffle under about 3 inches of fast moving water. It receives 50 PAR of overflow (pink) light from my Cheato grow section. It breaks all the rules that I was taught. I was looking at them yesterday and they are growing and have good polyp extension. It has lead me to believe that coral frags can adapt and thrive in several environments pretty quickly. I will never claim wave surge is not good for corals. My personal feeling is that there is a little too much marketing directed at it.

I agree about the loc-line. The physics of eductors is pretty well documented. My experience with them is only from experimenting with them observation of flow. I do not have a flow meter to quantify it. I prefer a large smooth high volume flow on my reef. DIY eductors have made this easy for me to achieve. If you have some experience with them I would appreciate more information.

Frankly - no clue what this post means -but it sounds reasonable.

 

[MnFish1]

what is a loc line?


\

 

[ca1ore]

My comparison was directed toward the behavior of directional water flow of any kind over uneven surfaces relate that flow to nutrient transport. Nothing to do with plant or animal growth. My intent was to demonstrate that any water flowing in the same direction over an uneven surface creates plenty of swirling eddy types of currents. I also hoped to express the possibility that this type of turbulent flow could keep sediment and detritus suspended in a reef tank as it does in a river, until it could land in a filter sock or some other area designed to manage it. It has been my experience that it works.

That wasn't necessarily clear to me from your post, but OK.

The physics of eductors is pretty well documented. My experience with them is only from experimenting with them observation of flow. I do not have a flow meter to quantify it. I prefer a large smooth high volume flow on my reef. DIY eductors have made this easy for me to achieve. If you have some experience with them I would appreciate more information.

There's really no way I know of to easily measure the induced flow from educators/penductors. I've used a few over the years on my closed loops; never on the main return because I want as much true flow as possible. The other issue with them is they can suck air if too close to the water surface (which is how I manage back flow on my main returns). I'm currently using a pair of the VCA nozzles. I mostly like them.

 

[w2inc]

what is a loc line?


\

It is a brand name for a product that snaps together to build a flexible flow tube. It is kind of a great concept but in most situations they do restrict flow. If power cost for your pumps is not a concern then you might really like what you can do with it. https://www.loc-line.com/products/34-loc-line-system/

 

[Brew12]

I'm another that has to disagree with avoiding laminar or gyre flow. I've only dove on a small handful of reefs but they have all had very laminar flow on them, generally in the direction of either the waves or the tide. The only areas I have experience true chaotic flow on a reef would be in extremely shallow areas near a shoreline.
It's one reason why I run 4 of the Maxspect XF250 gyres on my system. I want strong laminar flow that I can periodically alternate. My personal opinion is that I get much better results than when I used more traditional stream pumps.

 

[eatbreakfast]

I have also found that laminar and/or gyre yype flows to be excellent for reef tanks, so wondering why one of the guidelines for flow advises avoiding them.

 

[Brew12]

I'd also say it appears the Mike Paletta agrees that gyre flow isn't a bad thing!

https://www.reef2reef.com/ams/mike-palettas-new-tank-is-up-and-running.646/

 

[MnFish1]

https://www.advancedaquarist.com/2007/1/aafeature

Here is a nice article that talks more specifically about 'types' of flow. I think it complements the great article by Cynthia. I personally tend to think that its not laminar flow that's the problem - its the 'speed' of the laminar flow. As many others have suggested - 'laminar flow' quickly becomes turbulent flow in a reef tank. The article above goes into great detail on this. I use Maxspect gyres on both sides of the tank. As it says in the article - most if not all flow that starts at the head of the source is 'laminar'.