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Flow and/or circulation

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DonW

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The advanced area is slowing down. I think we need a new topic. Flow and circulation is something I think alot of folks under rate. For the most part I dont think that people have enough. My current tank for example does not have even close to enough with two Mag24 pumps. Sounds like alot 4800 GPH, 100 gallons of water thats 48 times turn over. The top of the water has a nice boiling affect and looks like there is tons of flow.
The reality is that after doing all the math, with those two pumps, I'm only getting about 19 times turn over per hour. Not enough for a SPS tank.
Maybe some of you plumbing guru's can help everyone understand what there flow is, should be and how to achieve it. Lets not redesign everyones tank, but take a look at what we have and help improve enviroment that were trying to recreate.

Don
 

Katchupoy

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I agree with Don. Also we need to learn what is more important.

Turn over rate? or
efficiency of the flow? (design concept on where we put our flow...)
 

jlehigh

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Great questions! One more: We know that too strong of flow can cause tissue damage to sps.

What are methods to increase flow while staying within a safe velocity for the inhabitants?

- Larger output diameter
- ???
- ???
 

DonW

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jlehigh said:
Great questions! One more: We know that too strong of flow can cause tissue damage to sps.

What are methods to increase flow while staying within a safe velocity for the inhabitants?

- Larger output diameter
- ???
- ???
I think the general rule of thumb for outlets ,is double the input. If you have a 1.5 then you would use 4 3/4 outlets. For the most part I think 3/4 is standard due to the fact that LocLine is only made in 3/4 or smaller.
Do these 4 outlets have more velocity than 2 1.5" outlets??

Don
 

Scooterman

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This is a good topic, so let’s see what we can discuss.

In my 5ft tank, I have about 45X turnover. There are always spots that lack good flow, so I have to watch those areas and accommodate cleaning when build-up occurs. I also have to watch what corals I place in the varying flow areas. Nikki has a great tank for looking at a well designed flow system.



http://www.reeffrontiers.com/forums/showthread.php?t=2062



Mike also had a discussion here………….



http://www.reeffrontiers.com/forums/showthread.php?t=2675





I find placement of flow is tricky & takes tweaking to get optimal flow. I use a Tunze stream on one side of my tank, it has great water movement, and I do need another on the opposing side to make a better motion but with the good flow comes a price. I have a stair rack system built along the back made of ½” pvc, where a 900gph pump sits directly underneath it blowing across the entire back said. Up on top my LR is layered on top of the rack, & up front on the glass, so it ledges up. My circulation is just enough to move water from the sump back. Like I said another high powered 3,100 Stream would probably be enough for that one small tank. I like the soft high volume water flow these things produce, I also have it on a pulsing controller which makes ripples of waves, can’t wait until I get it all set-up the way I need.
 

reedman

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The size and number of outputs is dependent on the pump output size for minimums. If you have a 1.5" output from the pump then you can calculate cross-sectional area to be 1.767 sq in. Then you can determine how many outputs you want and what size (determined by how focused you want the output stream to be). In the example that Don gave with 3/4" outputs, you have a cross-sectional area of 0.44 sq in for each output. As a result, to not have back pressure on the pump you need at least 4 outputs (3/4" ea) giving you a total output cross-sectional are of 4 x 0.44 sq in = 1.76 sq in.

To decrease velocity you can:
have more outputs
larger outputs

To increase velocity at a particular output you can decrease the output cross-section, but remember to compensate for that elsewhere unless you have a pump that can handle back pressure and you want that.

Also, keep in mind that it is not just a question of velocity, but of variable output. If you have an output that changes the angle or direction (ala seaswirl, D-swirl, ocean motions, MBV) than you can have a higher velocity without damaging a coral. Think about the velocities a coral experiences when the waves crash on them. Much higher than we could ever introduce into our aquariums, but for a short duration. This clears stagnant water and removes the microlayer around the branches.

Random water flow is a key component that is often overlooked in the quest for very high turnover. Laminar flow is almost useless for a reef tank, so you need something to create that random flow. There are more and more options on the market if you have the money to spend. Otherwise you get creative in laying out outputs, making your own device (like Don did), or implementing something that is not at all designed for aquarium use (one of my personal favorite past times).

The qwest for the Holy Grail continues. Enjoy the journey all.
 
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mojoreef

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Flow is an important function in our reefs, but I believe it is not understood the way it should be and really should be looked at as a biotype. One should really go back to the locations from which the corals strive in to get a good grasp at what their used to. Then try to break down what the flow does for them.
In the case of a sps type tank, we can see that good strong flow is what they prefer and where they tend to strive.Corals will also evolve (even in our tanks) to the flow at hand. A strong more direct flow will cause them to thicken up and create thicker slime coatings.
Corals need flow in the wild to remove nutrients that come from the area in which they live (lots of fish), also it keeps them clean from the waste and detritus that they are subjected to. When waste/food/detritus lands on a coral bacteria begins to reduce it, the tissue below the W/F/D begins to weaken and is shielded to the light it requires. In most cases the bacteria continues past the W/F/D and into the tissue of the coral itself. Bacterial infection is a leading cause for these types of corals to go south.
For me their are three areas I really look for when designing or trying to get flow in my tank.
The first is the bottom. In this case I try to make sure that the bottom of the tank is fully covered. As in no dead spots and no places for the W/F/D to build up. What this gives me is less areas where the W/F/D collects and also keeps it in the water column where it can be used by the corals and such as food.
The second area is the mid and upper levels.These areas are basically the areas where corals are and the vast majority of the rock work. This area is a little tougher. What I try to accomplish is a good random/alternating current. Not really looking to cover all areas as much as to keep them clean and free of the W/F/D. To accomplish this it you are not really looking for strong flow as much as alternating flow. With strong flow in this area you can run into a few problems. On is to much direct flow on the corals tissue, which will lead to recession. The other is having flow going one way does not mean you are going to remove it from the surface of the rocks or corals, usually it will just fall into a position behind a branch or into a cranny/nook. Having flow bounce back and forth is far more effective in removing W/F/D.
The final area is the surface of the water. In this area I take care of it mostly with the long coast to coast overflow. It creates a constant draw which pulls the surface of the water off and into it. I also use a few heads to accommodate it and to agitate the surface a bit.

Mike
 

reiple

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just a little tiney weeney more info about flow ....

corals/reefs are even referred to as walls of mouth. thousands upon thousands of polyps open to eating whatever flow brings to them. depence is high as these animals are generally immobile.

hence the importance of proper flow. ;)
 

NaH2O

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In the case of a sps type tank, we can see that good strong flow is what they prefer and where they tend to strive.
This is one example, IMO, of why a tank would benefit from being 'type' specific (i.e. SPS tank, Softie, LPS). I don't think I'd be very successful at keeping a softie up on the rockwork in my tank. (although the nutrient problem I have may serve the softies well :) )

Here's a question I have. This isn't to debate between the oceans motions or motorized ball valve, as either is great. What benefit does the MBV have over the OM or vice versa? For sure the timing control on the MBV is great, but how important is this feature?
 

Llarian

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Nikki, that icon is just disturbing.

The more time I spend thinking about the "biotope" concept rather than even saying you're doing an SPS or LPS or Softie tank, the more sense it makes.

An upper fore-reef/reef-crest is going to have more surge, and stronger directional flow from waves crashing over it than, say, a mid fore-reef or back reef slope.

Rubble zones will probably have more random constant flow than surge due to being somewhat protected from direct waves.

There are SPS and indeed some of the same Genera in nearly all these zones.

The major complaint I've heard about the OM so far is that with a 1rpm rotation, the flow is cycling every 15 seconds on the 4-way, and every 8 seconds on the 8-way. That's been stated as cycling too quickly, but assuming you could push enough flow through, that's probably about right for something like a reefcrest. A slower change, achievable with the MBV, might be more appropriate for a location where changing currents and things of that nature come more into play than surface waves.

And the more I think about it, I don't think either is necessarily appropriate for a back-reef slope or lagoon, as it would seem to me that you'd get better random flow using multiple always-on outlets that converge and cause eddies and random flow that way rather than by actually switching.

Just some conjecture. =) I'd be curious as to Anthony's opinion on this as well, as he seems a big proponent of more constant flow rather than switching.

-Dylan
 

DonW

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I think the MBV is just plain more user friendly in terms of plumbing and control. What I wonder is why most people run such low flow. When I was deciding how to plumb my tank, I looked at other tanks. For the most part the very successful ones are running huge turn over rates. Many times higher than the "suggested rate". Sure there alot of nice reef with lower rates. Are they working alot harder to keep them that way? 20 to 30 seems to be about average. Are the 60 to 70 times per hour turn over rate tanks healthier mostly because of this high rate?

Don
 

mojoreef

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Again Don it brings us back to biotope. For corals that rely of food capture, to much flow will make it alot harder. How a coral cleans it self or if it can clean itself pertains to.
Heres a reverse way of looking at it. the enviroment dictates what coral lives or dies thier. Create a high energy enviroment with strong lighting and the corals that grow thier will be mostly SPS. create a low flow, high divercity, high nutrient enviroment and your soft corals will thrive. Simple as that.

Oh on the turn over rate its not so much the ammount as it is the effectiveness of it. Alot of folks flow rates are not that effective or dynamic, so they have to over power it with alot of flow power/



Mike
 

DonW

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mojoreef said:
Again Don it brings us back to biotope. For corals that rely of food capture, to much flow will make it alot harder. How a coral cleans it self or if it can clean itself pertains to.
Heres a reverse way of looking at it. the enviroment dictates what coral lives or dies thier. Create a high energy enviroment with strong lighting and the corals that grow thier will be mostly SPS. create a low flow, high divercity, high nutrient enviroment and your soft corals will thrive. Simple as that.

Oh on the turn over rate its not so much the ammount as it is the effectiveness of it. Alot of folks flow rates are not that effective or dynamic, so they have to over power it with alot of flow power/



Mike
I understand the whole biotope thing. Your tank for example is a sps type biotope. I read somewhere your pushing about 35K GPH about 60 times turnover per hour. Its obvious that the beast is a successful reef. Then you see much smaller systems around 120g with 3K gph flow less than 30 times turn over. Is it the additional flow that is the main contributing factor to the success? Imagine cutting the beast back to 17Kgph would this still work as well?

Don
 

mojoreef

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Actually the beast runs at about 35 times turnover. IMHO its to do with the effectiveness of the flow. The flow is designed to do a particular job, if you can do it with less then its still effective. You can just take a run at it with large numbers when it comes to flow. I do agree that tit is important and most folks don't use it like it should, but I think for it to be done right one has to approach the tank to accomplish the tasks at hand and their are allot of variables.
Just the amount of rock will dictate that, and the placement also. With no rock you could cut the overall flow down to very little, so your flow could be anywhere between little and a ton just based on the layout and amount of rock present. Then their is sand, it plays a simular role but opposite. You also have to consider the output style, you could only have 2 outputs with a ton of flow and put that up against a tank with say 10 outputs and lower flow and it would win as it has more of the tank covered for the tasks at hands.
This is why I like to promote the effectiveness rather then the overall amount.


Mike
 

NaH2O

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Llarian said:
The major complaint I've heard about the OM so far is that with a 1rpm rotation, the flow is cycling every 15 seconds on the 4-way, and every 8 seconds on the 8-way. That's been stated as cycling too quickly, but assuming you could push enough flow through, that's probably about right for something like a reefcrest. A slower change, achievable with the MBV, might be more appropriate for a location where changing currents and things of that nature come more into play than surface waves.
Good thoughts, for sure. I wonder though, in an 8 or 15 second cycle, if the output is one that will be beneficial in carrying away waste products, etc. or enough flow, which brings us back to effectiveness.

How do we know if our flow is effective?? What types of things do we look for in the system? Does it depend on what you are trying to accomplish?
 

forsaken541

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Here is also another subject that would interest myself and some others I am sure. Not all of us have an acrylic tank and are forced (for the time being) to used sumpreturns and PH's to create the flow for our systems. I would love to get some opinions on placement, size, and outlet type for we lowly PH users. Thanks,
Erik
 

reedman

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Hey Erik,

As far as placement of PHs, it's very similar to placement of outlets for a closed loop. First thing is that it depends on what you keep. Typically you will want two PHs in oposing corners pointing at each other to create a chaotic/random flow. After that it really depends on the layout of your rock work. Your goal should be to minimize/eliminate dead spots in the hope that you can keep all of the nasties in suspension until they are removed via the skimmer (or other means).

As a side note, you are not stuck with PHs alone just because you have a glass tank. I too have a glass tank, but I have an Ampmaster 3000 external pump plumbed up and over the tank lip that I use as a closed loop system. This was one of the best additions I ever made to my tank. You are only limited by how resourceful you want to be. You don't need an acrylic tank to have the same type of setup as someone who has an acrylic tank, just some imagination.

Good luck.
 

mojoreef

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How do we know if our flow is effective?? What types of things do we look for in the system? Does it depend on what you are trying to accomplish?
If you look back a few post I give an exampl of what I look for in flow.


Mike
 

NaH2O

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I read that post, guess i need to read it again, as it was more of the reason i asked the question. I'll go back to it.
 
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