# Very low flow or very High Flow...which is best for plants?



## mwebb (Jul 17, 2011)

I always thought that in a CO2 injected tank, the flow and surface agitation should be very small. I have a 54 gallon bow front with an Eheim 2026 Pro II and have the flow rate at a little less than half on the flow meter. None of my plants move except the rotala that has grown up where the return enters the tank. However on another post I read some comments to a posters question about correct flow rates and one response was the palnts should move somewhat in the current in all parts of the tank. I am a little confused now. Should I increase the flow to a much higher rate in my tank to get all plants moving? I thought the lower flow rate was supposed to be better for the plants since it saves CO2. Have I been wrong and should I kick up the flow on my filter to give better circulation? I removed my spray bar years ago and just let the open end of the return dip below the surface a few inches for the outflow. Is there something better than this or maybe even a way to use the spray bar in a better way? It is a corner tank so placing it on either side isn't that great. I just let the intake drop into the back where the two side meet to form the corner and flow forward to the bowed glass in front 
Thanks in advance


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## jcgd (Feb 18, 2004)

You want to keep the surface agitation down. IE, no splashing. In my experience ripples and waves aren't a big deal, it's the water breaking from trickle filters and having the water level below the filter return that causes the CO2 to gas off.

It is somewhat personally choice, but you generally want good flow throughout the entire aquarium - under the surface. Having all the plants wave in the current is a good way to see if there is good flow because it's a visual cue. This helps disperse the CO2 in the water, as well as oxygen, nutrients and all the other good stuff. Personally, I think the only thing you should lower flow for is the fish. If they are getting pushed around too much it could be hard on them. If they look like they have no trouble fighting the current and have places to rest it should be fine.

Try to figure out what the flow in your tank is doing. If you can't get good circulation with only the one return, you might want to consider adding a powerhead to blow across the front of the tank as well.


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## Booger (May 17, 2004)

Turn up the flow *and* the CO2.


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## VeeSe (Apr 16, 2011)

Booger said:


> Turn up the flow *and* the CO2.


I agree with this. I always try for high surface agitation in my tank and make sure that the entire surface is rippling to ensure good oxygen transfer at the surface.


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## mwebb (Jul 17, 2011)

Thanks for the input. I will kick up the flow and watch the fish to see if they are doing OK with it. Also I see a lot of stuff on these glass lilly pipes. In particular the return one. It seems to have a very large mouth at the end of the out flow. Is this something that is beneficial or is it mainly more of a visual thing for the smaller rimless tanks I see discussed on here sometimes? They do look very nice and I can see why they would look good in the tank but would something like that help my 54 gallon or should I try to rig something up with the spray bar?


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## VeeSe (Apr 16, 2011)

The wide mouth is to distribute the return flow so that it's not all shooting out of a very small diameter (relatively) pipe outlet. Your spraybar does this by having multiple holes throughout the bar.


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## idontwan2know (Jun 8, 2011)

I'm new to planted tanks, but I think the ideal situation is a high volume, low speed flow. This ensures that you're getting movement throughout the tank, no dead spots, lots of filtration, etc. without blasting your plants and fish with a high speed/pressure current.

The key is to understand that speed and volume are two different things. A powerhead with a given flowrate and a canister filter and spraybar with the same flowrate will move the exact same amount of water, but the power head will look like it has more "flow" because it's faster and more concentrated.

_-- Sent from my Palm Pre using Forums_


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## jkan0228 (Feb 6, 2011)

idontwan2know said:


> I'm new to planted tanks, but I think the ideal situation is a high volume, low speed flow. This ensures that you're getting movement throughout the tank, no dead spots, lots of filtration, etc. without blasting your plants and fish with a high speed/pressure current.
> 
> The key is to understand that speed and volume are two different things. A powerhead with a given flowrate and a canister filter and spraybar with the same flowrate will move the exact same amount of water, but the power head will look like it has more "flow" because it's faster and more concentrated.
> 
> _-- Sent from my Palm Pre using Forums_


That is exactly what Koralias do. High volume, low speed.


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## Wwh2694 (Dec 14, 2010)

The problem with korailas is the flow is concentrated in one direction not wide ended up with dead space if both ur filter output is in one direction. U need to put ur pump on both oposite end to better circulation or u can just get a vortech pump .


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## jkan0228 (Feb 6, 2011)

You could have you're outflow at the top right of your tank(from an aerial view) and have our inflow on the bottom left and have a koralia on the bottom right blowing toward the inflow


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## Jeff5614 (Dec 29, 2005)

High volume, low velocity flow directed like this works for me.


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## HD Blazingwolf (May 12, 2011)

Flow is importAnt and so is surface agitation! Will you off gas? A little but it far outweighs the benefits of increasing oxygen levels in you tank. C02 is cheap. Having at least a little surface agitation will keep off gasing to such a minimum you wont even know the difference, and will improve plant, fish, and beneficial bacterial health and productivity. C02 isnt the one all be all of plant care, important? Yes. But it has to be balanced with a few other things, oxygen is primary as much as is c02


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## Steve001 (Feb 26, 2011)

VeeSe said:


> I agree with this. I always try for high surface agitation in my tank and make sure that the entire surface is rippling to ensure good oxygen transfer at the surface.


There's no real need for good surface agitation. CO2 and O2 will outgas naturally and quickly. They are gases and are a great deal less dense than water.


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## Jeff5614 (Dec 29, 2005)

Steve001 said:


> There's no real need for good surface agitation. CO2 and O2 will outgas naturally and quickly. They are gases and are a great deal less dense than water.[/QUOT
> 
> Afterall, just look at a good stagnant pond with no surface agitation. Nice clear, well oxygenated water, teaming with life, huh?


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## 150EH (Dec 6, 2004)

Flow from filters, circulation pumps, surface agitation with out breaking the surface tension, air stones after lights out all equal more oxygen in the water column which will help in bacteria health and production is good for fish, plants, and water quality, adjust the CO2 accordingly.

It used to be popular to put your spraybar above the water surface, hence the name, now with CO2 added to the water most have lowered the spraybar below the surface to get the biggest ripple effect you can without breaking the surface, surface movement is important to O2 exchange and helps to keep away surface scum.

I still see beautiful dutch tanks on youtube with 2 outlets from 2 Eheim 2262's an inch above the waters surface, they may just be cranking the CO2 a little more.


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## plantbrain (Dec 15, 2003)

The nicest places where plants exist are typically Springs with velocities about 1 knot. Slow even flow, very clear water and rich in CO2.

Tide pools and ponds can look nice, but, it depends on the temp and time of the season. In the later stages, they look terrible : are entirely covered with weeds and algae. Early on, say April, they can look nice. 

So when you are speaking of, matters also.

Still, I've seen nice planted tanks with little flow, but very few and robust fish.

I have yet to see a nice planted tank with little to no flow and a lot of active fish stocking.

Given that both can be done, and one can allow for more fish and nicer stocking, less issues with gassing the livestock, I'll gladly opt for more flow thank you very much.

Would you have a fish only tank with very little flow also?
Probably not, so why do it to a planted tank?

Also, if you look at those foul covered ponds, there's no fish under those mats, they are all dead froma lack of O2. You might have some guppies or catfish, a few that managed to make it through.


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## Booger (May 17, 2004)

Tom,
What are your feelings on the relationship between flow and nuisance algae? My tanks have >10x flow and somewhat open aquascapes, but I can still find little dead spots as they are the only places where I see GDA.

My newest 65 gallon setup has very strong flow, but there is a small 6"x 3" spot that is blocked by the hardscape. No easy way to get flow there without a vortech. Not coincidentally, this is the only place where I'm seeing algae.


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## Steve001 (Feb 26, 2011)

Jeff5614 said:


> Steve001 said:
> 
> 
> > There's no real need for good surface agitation. CO2 and O2 will outgas naturally and quickly. They are gases and are a great deal less dense than water.[/QUOT
> ...


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