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Mind you, I said flow not surface agitation. Not concerned about CO2 blow off.

This is a topic I don't see discussed much but that I think it is important for many reasons.

How much flow do you have?
 

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I think that a good flow rate is a factor that depends on the positioning of the filter in- and outflow.

I got a 180 gal. tank that you may have seen in the DFWAPC gallery. It has all the original hardware that Jeff Senske had put on it. It has 2 big Eheim canisters rated 315 gph each, but the actual flow that enters the tank is barely 120 gph from each filter because of the hydrostatic head ( i checked it with a gallon jug and a timer). So with 240 gph in a 180 gal. tank the flow is just a little above 1x the tank volume.

The tank has no dead spots even when it's thickly planted. The tank is drilled on the bottom in 2 places. The water from the bottom left is being pumped in the top right. The water from the bottom right is being pumped in the top left. Basically and "X" pattern.

A standart 55 gal. tank equipped with a 160 gph Fluval (probably barely 80 gph at with 4 ft head) ends up having dead spots and uneven temperature. And that is 3x the tank volume. That is why I think that positioning the in and outflow (and not the flow only) is very important.

Also - a spray bar is not "a cure for all". I have a 120 gal tank that is about 1-1/2 ft wide. and has one of the new 250 gph Eheim (the one with the internal heater). Only after adding an HOT Magnum to the tank I resolved the dead spots problem.

I bet someone will mention the Squid gizmo that gradually alternates the flow from one to another outlfow pipe. I tried to hook it up but I hate the looks of it inside the tank so I removed it. It may work very well I'd like to hear about some experiences with it.

--Nikolay
 

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Niko,

Boy, that's not a lot of flow you have there.

Flow is important for a number of things:
  • proper gas exchange at the leaf surface;
    healthy and natural environment for the fish;
    avoiding temperature differentials;
    quickly distributing nutrients in the water column;
    minimizing detritus buildup;
    increase plant tissue exposure to light (i.e., plants moves and exposes more of itself to light);
    among other things.

Certainly a machine like the SCWD (Self-Circulating Water Device- I think) could create a nice back and forth flow. It may or may not be natural in your aquarium. I too agree that its placement can detract from the aquascape.

Can anyone think of how flow can be increased without compromising aesthetics?
 

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I'm curious as to this flow question as well.

My 7 gallon gets a nice bit of flow from the waterfall in the AC Mini filter, but I am looking for a better filter with more flow and something that's not really HOB. I'm considering a smaller canister filter (smallest I can find?) and right now am stuck at 80gph. My question is ... is this too much flow for a small tank like this? I guess I am wondering how much flow is good, and how much is too much - especially when you want to keep fish that are used to slow moving/still waters. In my case - Licorice Gouramis.
 

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We have a planted 90 gallon tank with just one small air stone driven foam filter. That's it.
Everything looks good and healthy... and the filter has never been cleaned since installed 3 years ago ...

Edward
 

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Art, I've always considered flow to be very important in my tanks whether they are high light, low light, or something in between. Insuring that mulm doesn't accumulate in spots, bring steady a supply of nutrient rich water to the leaves (overcoming the Prandtl boundary), and to eliminate stagnate pockets where BGA likes to gain a foothold are some of the reasons why I like plenty of flow in my tank. Personally I prefer to reposition my filter discharge pipes around the tank weekly with my water change. I also run smaller but redundant filtration on all my tanks that are 30 gallons or greater. I don't preach these views, they are just small nuances that I've found that produce good results in my tanks.
 

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Flow rates in an aquarium also depend on which plant species you are keeping. Bolbitus heudelotii and Anubias sp. certainly prefer flow rates higher than most stem plants like Ammania sp, Rotala sp., and Ludwigia sp, IME.

Carlos
 

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Hi all. I want to put forward here also bad consequences of flow: I've observed that where there is a more directly impact of water flow (even not very high flow) on broad leaves the population of epiphytic algae increases so much. I think there is a direct relationship between the stabilization of the boundary layer over the leaf and flow. Art quote as a flow important influence
proper gas exchange at the leaf surface
. No movement implies a broad boundary layer where the gases levels (O2 and CO2) gives a fall of the photosynthesis rate for the plant, but this also affect (and very much) to the algae which live over the leaves, which are the best favored by the change of water near the leaf surface by flow.
Regards. Maurici.
 

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Maurici,

Particularly in broad leaved plants, lowering the size of the prandlt layer increases the exchange of O2/CO2. Photosynthesis is enhanced as a result of increased ability to uptake CO2. This strengthens the plant and should increase its ability to comabt epiphytic algaes.

My experience, specifically with anubias, is that current lowered the incidents of green spot algae. I wonder what others have experienced.

Saludos,
 

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My experience, specifically with anubias, is that current lowered the incidents of green spot algae. I wonder what others have experienced.
That's a great observation, Art! When I was raising my phosphate levels in an effort to lower the amount of spot algae on my Anubias leaves, the output of the canister filter was flowing right over the Anubias leaves. I think both high phosphate levels and good water flow have something to do with it.

Carlos
 

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I agree, Art, it seems clear that there exists a photosynthetic improve of the plants population by enhancing the CO2 uptake, but I have some doubts:

1- is possible that we interpret the algae decrease associated at a higher flow as a final step and it is only a change of species which needs more time to give an observable algae cover? The next populations of algae will be more adapted to higher flows. Eg. reduction of spot algae, slow but continuous increase of beard algae.

2- I don't see clear how this algae reduction operates. Locate me as an small algae on the surface of a leaf where I have some hard troubles for compete successfully: the prandlt layer poor on CO2, the possible chemical defenses of the plant epidermis to my attachment, the uptake of resources by other places of the plant (roots, other leaves,...) which let them out of my possibilities.
- Then, you make thinner the prandlt layer (and I'm in direct touch with it) so, I (the algae) will be the first one to celebrate the gas and nutrient absorption improvement.

Nevertheless no, this is not what we see; our observations are a plant improvement and an algae retreat.

The overall explanations I found are that algae are handicapped when the conditions are good for plants, mainly by a massive plant uptake of nutrients, is it enough for you?

Saludos.
Maurici.
 

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As water flow increases, the amount of periphyton growth decreases.
Hence, they are inversely related.

An interesting study from Hopson and Zimba here at UF tested periphyton removal by taking a plant covered with epiphytes and swirling it in a flask for 90 secs removed roughly 88% of the epiphytes.

I swirl my plants around when I replant, get new ones from the wild etc. I do not dip them in anything like bleach etc.

I think good even flow is the key.
The actual volume/time itself can be misleading.

The other thing, if your spray bar has outflow from the back bottom section of the tank, this hides the spray bar, it also sends high CO2 rich water underneath the plant's leaves.

Why is that important? Guess where the stomata are that take in the CO2 gas? On top or the bottom of the leaf?

So current coming upward along the bottom back wall directed out horizantally along the gravel's slope towards the front of the tank is one of the best flow designs.

But you still need some surface movement also. Folks with surface sucking prefilters need not worry about that though.

Another issue has not been addressed here. Tank size/lighting etc.

A 20 gal or less is easy to saturate with CO2 rapidly with little mixing.
Trying this on larger tank will be more problematic.

Lighting increases will cause more CO2 uptake and more CO2 demand.
You will need CO2 to the plant leaves with more light.

If you look back at many past tanks with CO2 say a decade ago, 15ppm was the max CO2 suggested. The lighting for the case studies in the PMDD article was quite low.

I essentially doubled the CO2 when the lighting I used was 4-6 w/gal.
30ppm is fully saturated even at full sun since the aquatic plants can only max out at about 30% full sun.

So flow is interelated with a few different things.
If you do not have driftwood, feed very much, have high O2 levels, lots of plants etc, you will not have much mulm either.

Regards,
Tom Barr
 

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I don't know if I completely trust the information on the Dennerle site.
If I click on the 'no tendency towards algae growth' link, it reccomends
what sound like commercial products they're selling e.g.
'Bodenfluter cable with low heat output'

From my experience, when I had a greendust algae issue,
areas of the glass that get very high flow rates across them
remained clear, while the other areas greened up. It's logical right?
The high flow rate does not allow any algae spores to attach to
the surface.

Interesting discussion..
 

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Tom,
I always thought directing the spray bar down 45 degree was the best design? The Co2 gets to the bottom of the leaves from the circular motion of the water, and the Co2 doesn't reach the surface as fast. With the suction at the bottom right, the circular motion is maintained. It seams that having the spray bar behind the plants would reflect the flow in unintended directions.
 

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Ghori's notion is correct, the high current prevents Akinsendesmus zoospores from attaching.

This alga is specific with respect to attachment once scrubbed off.

It seems to grow in a few minutes, but is merely reattaching back to the glass.

IU, no, the flow pattern depending on the CO2 input method. Pattern A.
If in line with the filter or with the sump, then the best flow pattern would be the lower direction towards the front on the glass.

This pattern would put CO2 where it
is most effectivem on the lower leaf, that's where the stomata which take in the CO2 are found, not the top of the leaves.

As far as Dennerle's site and info, I've made some critical comments in the past on AQ's forum,


I would bet a wooden nickle I've done far more research than any of these companies or all of them combined with respect to algae and plants.

If they really did the research, don't you think they would have figured out a lot more and reduced the cost by now??:):):):):)

Instead they come out with a new algae cure or product that reduces, retards etc every few months/years.

Gotta make some$.

My methods/suggestions do not make much, but SeaChem sells some of the stuff that actually works.

Greg knows I'm not telling folks to buy RO etc, but they still can suggest it for the person that really wants it.

They will not say it reduces algae in planted tanks vs tap water either...........

Being critcal on an idea or a statement does not imply that I dislike
or have it in for these companies like ADA, Dennerle, Dupla, Algae fix, etc they would have difficult time refuting my comments though.

Their goal is to make $ and meet consumer demand.
. Mine is to find out why and how algae and plants grow well in marine, non CO2, CO2, brackish etc systems.
I share willingly my findings and try to help others muddle through all the hype.

So there is going to be disagreements and conflict.
I'll get a book out sometime next year, so we will see how they respond then.

Regards,
Tom Barr
 

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well as beard or hair algae goes... everytime i have ever seen it it starts near or directly in the high flow areas and the heater. everytime. so this cant be entirely true, i mean we combated it by waiting for it to grow on and around the powerhead outputs, and cleaning the powerheads we eventually defeate4d it, but it was the only way i could get it too work, well otos are known for eating it. just an observation
 
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