I wanna talk about flow.

[Detri]

Flow is a HUGE subject anywhere you go. I just wanna hear a few thoughts and talk about it openly. I have been doing a bit of experimenting myself lately. A bit of research and learned alot. So far. I wanna learn more.

Lets start this thread with a question.

Have you ever looked closely at a real Reef? Which ways does the water flow around the corals?

If you look closely, you can really tell the way the corals and fish are being manipulated by the water. It has alot to do with Reef shape too. There are a few reef that play exception to the rule. Hopefully this thread will help everyone with rock design and flow with less effort.

 

[spongebob lover]

I'll tag along for this one dood .
I have never seen a reef in person so i have no clue on how the flow goes around them.
i believe it's not about how many powerheads you got in a tank or how good is your closed loop, if you don't have the right aquascaping to let the flow go through it .
I can be wrong but let's see what the experts have to say .

 

[Brenden]

Wasn't Flow the waitress at Mel's diner?
For a even better idea of flow try scuba/snorkeling on a reef. It will beat you to death. Seems the more random turbulance the better.

 

[Detri]

But, it's not so random right on the reef. It is very turbulant near the surface.

What gives the random flow is the back wash of water coming over the reef and the water coliding with it toward the reef. Or across the reef. It basically comes from 2 directions with the majority flowing over the reef.

 

[ronj]

i just went snorkeling the other day....i was right up against some huge rocks ... i got slammed into the rocks several times... my finger tips are still cut up from trying to anchor myself to one of the rocks..the current was very strong.. i was in water from 3-8 ft

 

[Brenden]

But, it's not so random right on the reef. It is very turbulant near the surface.

From my personal experience I would disagree with that. The larger rocks/reef re-route the flow/currents into each other making it impossible to perdict direction of the currents.

 

[Krish]

From what I've seen and experienced, It's a continuous sway from side to side that I mostly see on reefs. The "tide" will determine what's going on as well. There is even a period of almost "stillness" called slack tide (which happens between tide changes that doesn't last very long) that almost feels like the ocean has become still. It is during this time that you can usually only catch certain fish like mutton snapper by line. Some people compare the ocean water movement as being turbulent which is cool, but I personally think of turbulent water as being violent water that is coming from every angle which would send you in any and every direction every second to the point where you couldn't predict which way you would be going had you been in the water. Yes, there are strong currents, but it's almost predictable once you've been in the water for a few seconds until the tide changes. If you were to lay on your back on top of the water, you would go with the tide that will take you in one direction (until tide chages) Same with being underwater out in the open water. Sometimes, we have to swim against the current a few yards off of a reef and then swim straight down and by the time you get down, the current has taken you right to the reef and then you'd almost have to swim against it to stay stationary over the reef. If it were random flow, you wouldn't know what direction to kick in because it would keep switching up on you, but it isn't that way...Atleast I have never experienced it like that under normal circumstances. Now when you go through "cuts" or "channels" sometimes there is crazy random turbulent flow that will drown you in a second if you aren't a strong swimmer. You have no idea which direction you are going and almost have to give up and let the current take you "wherever" otherwise you'd get exhausted trying to fight it. I'm not sure if the land on either sides of the "cuts/channels" have something to do with it, but the water usually looks kinda glassy with surface aggitaion which will show you ripples in some places and then a swirling action in another and you can tell just by sitting there looking at it, that the water has no source of direction... Just a few of my observations living on an island. Some people may think differently than I do which is cool, btu I figured I'd just share my own personal thought

 

[ronj]

i also believe the rock structure or reef structure determines the flow

 

[oldsaint]

Did anyone catch Jake Adam's lecture at IMAC "Water flow speed is critical"? It was very interesting. He determinded the ideal flow is 7cm/sec across a coral and alternating lateral flow is better than random turbulant flow. Sorry, for some reason I can't find my notes but if someone else was there maybe they could elaborate.

 

[shallowreef]

I like this thread so i am just going to follow along.

 

[Scooterman]

He determinded the ideal flow is 7cm/sec across a coral and alternating lateral flow is better than random turbulant flow.

That is what the MBV does with the plumbing design I have, the flow moves in one direction then back the opposite, also according to what rock structure is in the way will affect that flow pattern.

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

 

[DonW]

One thing to think about is how the corals grow with different types of flow. My tank for example has lots of continious flow. Looks real cool but the corals really are ugly. Digitata for example grows only out, flat across the rock work like crab grass. Monti caps will only encrust the rock and never grow upwards.

Don

 

[Herefishyfishy]

Just got back from Jamaica, snorkling and scuba. Scuba depth from as shallow as 40 feet to shipwreck dive to 110 feet. Currents and eddys changing steadily at all depths. Snorkling into and through reefs from as shallow as 18" to as deep as 30'. Hard to generalize the flows on the word reef. Some reefs are walls, some are flat bottom, some are heads, some are caves. The tides are predictable along with the general direction of water flow over and through the entire area, but as to specific locations, all bets are off. Picture a section of reef with caves and walls being in a wind tunnel and imagine the turbulance and eddys. The only thing that can be counted on is the lack of predictability on water flow. In a tank, without surge controllers, the currents will be more predictable, but there are even changing patterns in the controlled condition. Put flake food in the tank and watch the swirls and flows as they change.

I probably have too much flow in mine. one Seio 850 and one 1100 plus the iwaki 40 pumping through unimpeded. Keep changing the flows and watch how things are doing. Seen some tanks with little flow doing awesome and some with a lot doing just ok. Generally, seems more is better up to the point of stressing the polyps. As for fish, gives good exercize and some sport. OMHO

P.S. on the subject of coral beaching, very little evident of bleaching anywhere in Jamaica, only saw or heard of a couple small heads bleached and most reef had a lot of vitality and growth apparent. Bleaching is not all over the Caribbean, just some areas but still a HUGE cause for concern.

 

[oldsaint]

That is what the MBV does with the plumbing design I have, the flow moves in one direction then back the opposite, also according to what rock structure is in the way will affect that flow pattern.

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

Great link thanks Scooterman it will make for some good reading later tonight. I also have a MBV but haven't installed it yet. I've saved some good links from here for reference. How often does yours cycle and do you slow that cycle down at night?

 

[Scooterman]

You know herefishyfishy is right, not two reefs are alike also corals don't all grow at any of these so depending what your keeping would also help determine what type of flow you wold need, as long as yo could figure that out.

 

[Krish]

Just got back from Jamaica, snorkling and scuba

I remember you were saying you were going to Jamaica! Sounds like you had a great time! Now where's the pics!


As for the flow again, I kinda find it hard to imagine turbulent flow in all kinds of directions without a violent storm...Atleast I've never experienced being pushed any and everwhere out in open water. The reefs do break up the flow some which makes it kinda random bouncing off, but you sit above a reef looking down, and the fish as well as softies sway back and forth, back and forth. The source of flow comes from one direction only and not opposing directions crasing into each other at the same time. Just look at the waves coming into shore...What I see when looking at a reef is basically similar to the video clip of the Tunze wave box. Just another observation of mine...People may not agree with it which is cool, but it is what I'm use to experiencing living here my whole life

 

[Herefishyfishy]

Hi Krish, guess it depends on which definition of the word turbulance you mean. I am not infering violent patterns, just constantly changing. Here are a couple difinitions I was refering to: The state of flow wherein the water is agitated by cross-currents and eddies, as opposed to a condition of flow that is quiet and laminar.

The chaotic twisting, swirling motion in flowing fluid.

In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time. Flow that is not turbulent is called laminar flow. The (dimensionless) Reynolds number characterizes whether flow conditions lead to laminar or turbulent flow.

Basically, there are so many dynamics involved in a flow over and through a randonly shaped reef, that at no time is the flow always predictable. Covered by the rules of chaos. Yes in a calm sea near slack tide a few feet below the surface, the water can calmly ebb and flow over a specific animal, but it is moving back and forth as opposed to being held in a set direction. Deeper water seems less chaotic. Guess we are saying basically the same using a different viewpoint. Want to see real chaos, go diving in the pacific NW and watch the water move! I am envious of your living there full time, but all locations have their own merit. No longer dive here, getting too lazy to suit up in a drysuit, 30 some odd pounds of weight belt, tons of gear and still freeze your hiney off when getting in and hypothermia if a less than perfect setup Yes the amount of life in the Puget Sound and NW Pacific is mindboggling, but most who gain in years or cash seem to prefer your waters Nothing like swimming in bathwater of the Caribe

Regards,
Mike

P.S. a few pics to follow, still settling back in and lots of backlogged work (sorry about uttering the W word)

 

[Krish]

Yeah, everywhere is different I guess. Just like how I described how things are through channels/cuts. I guy I knew drowned through a cut because the current basically sucked him down and he couldn't fight it. Land plays a big role as well. With so many little cays surrounding one another here can change up the pattern a bit in some areas like these "cuts", but where I'm use to going, isnt surrounded by much so not as many factors affect the flow pattern.

Peace in the middle east!

 

[Detri]

This thread is turning out great!

I have my controller running a wave maker pattern with a couple MJ 1200 power heads across the top of my tan going over my rock from behind. There is constant movement. My Monti is starting to extent upward as well as outward from where I placed it.

I do also have continuos flow from my return and closed loop.

What most of you are saying is we need to spend more time thinking about our rock work to have the rock work to give it a job and more practicallity?

 

[ronj]

i think i am going to go with bare bottom for my new tank....i want my flow to go through the rock work and under it