Please explain water flow

[DonJasper]

I should admit from the outset that I'm beetleheaded enough that I have a hard time telling the difference between pebbles, gravel, grit and sand.

So when I hear you use a phrases like 'dreadful laminar effluents', and 'Produce random turbulent flow' my eyes glaze over.

For example, for someone of my limited Merriam-Webster experience the terms of 'turbulent' and 'flow' appear to be pretty near to being a contradiction in terms! When applied to a description of moving water anyway.

I've got a toy propeller attached to a powerhead that acts as a 'water fan'. I've got a pile of rocks in the center. So my tank looks like a big whirlpool. The powerhead side flow looks 'choppy', but by the time it swings around to the other side, it looks pretty 'smooth' to me. It's full top to bottom movement - even under the powerhead, due to the fact that the water there is being sucked into the propellor.

When I first started it up, I noticed a huge dust storm of shi... cra... detr ... dutrees ... stuff being kicked up from the rocks and sand. But is this an example of 'dreadful laminar effluents'??? I don't mean to be hanging on your every word, but could you please describe in more detail the kind of water flow you advocate.

PS - Feel free to use big words, I've got the Merriam-Webster website opened in another window, and I'm not afraid

[JB NY]

laminar flow refers to having all the flow going one direction only.

Random flow has to do with flow coming in multiple directions.

Here is a good thread on proper water flow for our corals. The thread is primarily focused on keeping sps coral which require much more flow that an average hard coral or softie tank, but the concepts should be easy to translate to almost any tank.

Let's talk about water movement in an SPS tank

HTH

[DonJasper]

Thanks. Didn't know the 'real' Trunze streaming powerheads had speed controls.

I've never seen a 'real' Trunze streaming powerhead in action. So I can't compare it to a DIY streaming powerhead that I whipped up last night . But I'd describe my cheap knock off as producing lots of flow going on one direction. So it would be a 'laminar' (well to some extent anyway). But Mr. Calfo has bracketed laminar with 'dreadful' and 'effluents' - neither of which is good company. Unless we start putting powerheads on little tractors and driving them around - I'd like to know that the second and thrid best options are.

[Anthony Calfo]

much thanks Joe!

Cheers, Don... as for creating random turbulent flow with less expensive leans (traditional/typical hobby hardware and applications)... you simply want to focus on creating flow with more than one source of water (like your prop pump only - that would be laminar).

Really... just as Joe stated, it is flow coming in multiple directions. Four small 1X sized powerheads would be much better than one 4X sized powerhead. Or... if using a sump pump, divide the returning flow into multiple tees.

Whichever way you go... have the multiple effluents aim to more or less converge upon each other to create a turbulent and random mix of water in many directions... rather than blast water from a fixed pump or powerhead aiming in only one direction.

Anthony

[DonJasper]

Thanks. Got it.

Since my curiosity is now aroused: Going to browse the SPS forum to see how many mount coral on their water squirting equipment!

[Anthony Calfo]

heehee... all good

[DonJasper]

I knew there was something left rattling around between my ears, but couldn't find it for awhile. Timing.

Getting the best performance from two water flow sources: One popular option is to get the flow to smoothly and gently alternate between the two. Is this better than to split it 50/50? How about turning on/off each source indenpendently in a complex pattern? (Sorry I can't bring myself to call it 'random').

[Anthony Calfo]

I'm not sure I understand what you mean by turn each on/off...

do you mean soemthing like solonoids/timers? If so, I would not advise it: overthought, unecessarily complex, and delivers less overall water flow than full-time converging effluents that produce random turbulent flow (the term is real my friend, if it matters to you... do consult oceanographic lit/refs, etc.)

Anthony

[sfsuphysics]

Oh, so random has nothing to do with the strict definition terms of the word? I figured turbulant was just some "wavy" type action, ie if your powerhead was pointed towards the surface (that'd be turbulant) or was pointed towards a wall/rock formation so that it'd break up the flow, but always figured random to mean needing to have streams oscillating from different directions, or have some sort of pump which makes good amounts of vortex action (tunze or to a less degree seios).

Hmmm this whole water flow thing is slowly starting to make sense, and I've been in the hobby a whole year now Although from what I hear the "Right thing" to do seems to change every two years

[Anthony Calfo]

the best way I can describe it (random turbulent) is like eddying currents... or the tossing of wheat in a field o a windy day... movement is active, but unpredictable/"random"

beyond that, my friend, you simply need to take the time to dive into a biology or oceanography reference, etc.

you really are making too great of a matter/deal of this

[sfsuphysics]

Gotcha, my GSP has that "wheat field" look already with 3 seio620s in my 135, so guess that's about all that was really needed.

Thanks for the help.

[Anthony Calfo]

excellent! Funny as it might sound, it really is a good analogy. Because without the whipping back and forth of water motion, some reef plants and animals cannot adequately purge metabolites/waste (as with laminar or linear flow).

Anthony

[wstellwagen]

As a phD statistician I must maintain that the term random cannot properly apply to water motion in a small box generated by mechanical pumps. It is no more random than psuedo random digits are random and has the same problems . Dead spots, areas of constant flow Perhaps small but real nevertheless

Walt

[Anthony Calfo]

really unbelievable...

Ahh... I didn't coin the term, and the majority of aquarists in the free world have no trouble accepting the term.

But if it will end this exercise in mental masturbation, please feel welcome to rename it anything you like and from this/that day forward... I will refer to it as such in the context of this thread just for you

The point of this rant being, that at some point (and that tolerance varies for each of us, of course), we should be able to recognize that there are certain points that are or become so staggeringly moot in the small or grand scheme of things that it really would be best to just save your breath/keystrokes.

There are better uses of your time, I am sure. And having just typed that last sentence, I realize I have posted and spent more time on the topic than I really would have liked/preferred. I value my time, respect yours and subsequently feel there is no need to debate or explain the term any further.

Walt... thank you for your input, but if we need a pHD statistician to proceed with running or counseling an aquarist on running a marine aquarium, the game is no longer fun

Rock on my philosophical brothers and sisters

Anthony

[DonJasper]

Ok waving wheat field. Got it. "Picture" is worth a thousand words.

Even though invertebrate zoologists get an honorable mention for describing conchs as moving by "saltatory locomotion", and not jumping. I award attorney's as the best class of wordsmiths that I know. One of them explained to me that she advocates defenestrating one's computer every now and then to maintain good mental health. As a computer professional, I then offered her the observation that the number of lawyers it takes to roof a house depends on how thin you slice them.

Now to put that small rock with ... uh oh. Xenia? Anthelia? < brown wavy fingering polypy thingys that loosely wave in the water > on it for a tank tour and see how things look. One corner has too much ... uh oh. Cyanobacteria? < reddish slimy mats with streamers flowing off them > and probably needs more ... uh oh ... attention. (whew!)

[Anthony Calfo]

heehee... I never get tired of good lawyer jokes

[lightngsvt]

So if I understand correctly, it would be better to have 2 powerheads pointed directly at each other on a diagonal, then to have 2 power heads on opposite side creating a "circular" flow?

[Anthony Calfo]

lightngsvt, yes... I do believe for most of the common/popular corals kept, this would be a better water flow. It is the very thing (converging power heads) that we did for so many years in the early days of reef keeping before there were so many novel water flow/movement options (surge devices, SCWDs, etc.)

Some corals specifically would suffer otherwise with laminar (via circular only) water flow.

Anthony