Flow patterns

[scottward]

I know this has been discussed before but thought I would create a new thread to kick of a discussion about flow patterns.

My tank is 6', about 400 litres. I currently have a single powerhead down one end pushing water along the length of the tank. I guess what is then happening is that the water flow is bouncing off the end of the tank and circulation back along the backwall in a more diffused manner.

I'm looking at buying a Koralia (or maybe two), to improve water flow in my tank.

What is the general consensus on water movement in a tank of this size? Would it be better to try to get two smaller flow patterns going down each end of the tank? Or would it be better to push the water more along the surace of the tank with the aim of having the flow 'fold under' at the other end and flow in the opposite direction at the lower level in the tank?

I have read discussions regarding putting all the plants in an 'island' in the middle and circulating the water around them. I suppose this might be the best option of all, but not necessary that artistic?

I have one side of my tank more densely planted than the other, typical approach for this size tank I suppose. What's the best way to get the water flowing around the denser foliage?

Scott.

 

[Biollante]

No Smart Folk, So Here I AM

Hi Scott,

I have been messing about with water flow options for the past 5 or 6 years.

I seriously doubt there is anything resembling a consensus view that suggests we really do not have a good understanding of the dynamics involved. I have built a few models as well as quite a few tanks. I use dyes track water flows, diffusion and disbursement.

For myself, I like dense growth; I put plant growth and happiness over aesthetics. I like lots of critters.

From the reef keeping community, I have embraced the “4-inch” rule. I work hard to keep flow open on the perimeter; I assume that is what you mean by plants on an “island.” I like high water turnover rates and I am currently running a couple in the 30-35 times an hour range.

It makes maintenance a little more difficult, but I prefer tanks at least 24 inches (61 cm) in width.

I have come to believe in a “downhill” flow pattern, inflow on one end output on the other end, with as little counter flow as possible

If it were possible, the “downhill” or output end would be a screen, allowing continuous, preferable pulsed flow. The “uphill” or input side upwelling with an imparted “low pressure twist” from the bottom front. The length of the “low pressure twist” is about 18 inches (46 cm) with another twist imparted every 18 to no more than 24 inches (46-61 cm).

The upwelling element should create simple ripples on the surface of the water. These days I prefer if to remove the water via an overflow across the entire end of the tank. In many tanks, this is not realistic for aesthetic consideration. Then the weir needs to be in the back corner.

I like to take excess water, equivalent to any extra flow generated power heads or eductors, pump that from the downhill side front, and run it back to the “uphill” back. This lessens the “bounce” and avoids counter flow issues.

I have also been running a perforated pipe down the center of the plant “island.” Variation on that theme include the use of drip system hoses and heads to distribute water directly into stagnant areas.

Biollante

 

[Tom Barr]

I have read discussions regarding putting all the plants in an 'island' in the middle and circulating the water around them. I suppose this might be the best option of all, but not necessary that artistic?

I have one side of my tank more densely planted than the other, typical approach for this size tank I suppose. What's the best way to get the water flowing around the denser foliage?

Scott.

I do this based on the flow, I trim the weeds back to allow for good long flow directions from one side to the other.

Some tanks have more open feel, this I like because I can see my fish and the current is good.
For thick wall of plants where less current is desired, I use a spray bar on the back bottom where you cannot see it since there's a wall of plants. Sort of makes hiding it easy.

That way the CO2 and flow comes up through the plant bed bottom up. Even flow etc, and the plants are not blown around much.
I still need good O2, which is tougher in such tanks, rarely or never seen: a packed tank with a high fish stocking, like a densely plants low flow Dutch tank for example.

For that layout, the spray bar along the bottom rear is a better option, a surface skimmer and a wet/dry with a dealed dry section and small overspill distance drop.
Maybe a little current in the upper parts if you have fish.


Regards,
Tom Barr

 

[scottward]

Hi Guys,

Thanks for the info, it has got me thinking.

I will be doing some 'doodling' on the train on the way home from work tonight...

I'll bounce my flow design ideas off you.

Scott.

 

[scottward]

Ok, so my tank is 72" x 18" x 24". About 400 litres (100g).

As per the crappy attached very quick sketch, I have a large clump of stem plants as indicated, everywhere else is E.Tenellus or large rocks, with a gravel only 'beach' area at the front left.

I think if I stick the 5000lph 'Koralia' (copy) in the back corner, I could get a flow pattern something like the red lines and arrows indicate? I would possibly end up with a second circular current in the front left-hand corner about the beach, but as there are no plants there I suppose I don't really care if the water just goes around and around there without actually mixing with the rest of the tank much.

In the back right corner, right down low, I would have an additional power head that does nothing more than mist a bit of CO2 fed into it's impellor and would use a spay bar to shoot this into the lower section of the clump of stem plants as Tom has suggested. I am aiming this into the direction of the main flow of course.

CO2 is fed in in 3 places, as there is a spray bar that runs along the back top of the tank shooting CO2 water from AM1000 into the back left, back middle and back right. The intake for the pump feeding the AM1000 is lower back right (near the extra powerhead misting CO2) as is the intake for my Eheim 2217 (which returns into the stream back right near the surface of the water).

Maybe I should set this up and take a photo! ;-)

Does it sound like I am on the right track to good CO2 distribution and water circ?

Scott.

 

[barbarossa4122]

Can't see your pick Scottward.

 

[scottward]

Let me try again with the crappy picture I drew...

 

[scottward]

Ok that seems to have worked this time. ;-)

The dark green section of the (overhead view) drawing represents a group of tall plants (vallisneria, h.difformis, l.natans), the light green section represent a carpet of e.tenellus. The brown area in the front left is an exposed area of the flourite substrate. Grey areas are large rocks. In the back left-corner, about halfway up, is a 5000lph koralia, pushing water towards the front right in a more-or-less verticle plane. In the back right-hand corner, only about 2 inches from the bottom, is a powerhead pushing water along the back glass back towards the Koralia. At the top of the water, pointing downwards, there are 3 evenly spaced CO2 returns (from AM1000). Also at the surface in the back right hand corner is the return from an Eheim 2217. In the back right hand corner are also the pick ups for the Eheim 2217 and the ocean runner pump that is feeding the AM1000.

Does this look like a reasonable flow design?

My biggest challenge at the moment is that powerhead in the back right hand corner. If I use another Koralia here, it is too spread out/strong for the tall plants (flattens them), but the Koralia has the advantage of not clogging easily. The powerhead in the back corner works ok, but it clogs easily.

Incidentally, I tried connecting a spray bar to the powerhead, but it seemed to kill off the flow too much?? Am I meant to be pointing the spray bar holes upwards (so that they are pushing the water up to the surface), or am I meant to be pointing the towards the front of the glass? It almost seems as if I need 2 powerheads here, one to feed the spraybar, and a second to ensure that water in general is being pushed through here.

Any suggestions?

Scott.

 

[barbarossa4122]

Koralias on sale until April 12th. I'll get another Nano.
http://www.fosterandsmithaquatics.c...&ref=6059&subref=AA&cmpid=E-_-FS-_-33010-_-P3

 

[scottward]

I ordered a cheap Resun 2000lph internal filter for the back corner of the tank, figuring I can fill the filter underneath just with bio-balls so that it doesn't clog too easily. I have also made a 2' long spray bar out of some pvc pipe. I'm thinking I will drill some holes along the pipe to turn it into a spray bar, but leave the end open to allow some of the flow to run directly along the back of the tank. Does anyone have any thoughts on this?