# How many times per hour should the tank turnover?



## duzzy

Hi there, 

I was wondering how many time should the tank volume turnover in a heavily planted tank turn over? and when calculating this do i include the sump volume as well as the tank volume?

Regards Darren


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## Tex Gal

I've asked this questions several times in different ways and never got an answer. On another forum I was reading about a tank Tom Barr set up a 180gal with a 2000 gph maxi jet. In addition his filters are 2 sumps. (I believe it's 2) It's doing beautifully. I think that was the most turnover I've come across on the forums. It was so much it stuck in my brain! I'd like to see what others tell you.


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## ed seeley

We've discussed this at UKAPS and we reckon to go for about 10 times turnover. Personally I've got a Juwel tank with a large internal filter that filters tha tank about 3.5 times an hour and a Hydor Koralia that turns the tank over just over 8 times an hour. So about 11.5 overall in theory. Once the media is in the filters though and they've been running for a while they lose a lot of this. Aiming for 10 times probably means you're about 5-7 times turnover.


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## houseofcards

There is no real answer IMO since every tank is different. Most I think would shoot for a turnover between 3 and 6 (effective not on the filter box) times per hour. Your really just need some flow in a well planted tank since the filter will actually be a small part of the filtration. I have 3 tanks that are runing beautifully on 1 turnover per hour. There is also theory the process of biological filtration is more efficient at a slower flow rate over the same amount of media.


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## hoppycalif

I have noticed that Tom Barr is now advocating lots and lots of flow in the tank, but that isn't like turnover, which is a terminology for filters, where water leaves the tank and returns. The advent of in-tank pumps or powerheads like the Koralia or the powerheads modified to use model boat propellers to move water changes the whole way of thinking about in-tank flow. It is one thing to have a half inch diameter pipe blasting 1000 gallons per hour in the tank, but an entirely different thing to have a little propeller moving a 1000 gallons per hour in a large diameter propeller wake. I think the goal is to have all of the water in the tank always moving, as if it were a river.


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## davemonkey

I once read that 3-4 times per hour was ideal (Aquarium Atlas by Riehl and Baensch, p.57).

I've gone with a 6 times per hour rule when I had fish-only tanks and that kept the tanks clean. The exception would be for large messy fish (like Oscars).

But in a planted tank, your main focus is on flow to keep the water circulated evenly throughout the tank (like hoppy mentioned with the koralia, etc...). I think that turnover per hour is less important because the plants in a heavily planted tank are a filter themselves. You'll get the turn-over you need with most any filter (within reason) if you focus on the current that your fish want and the circulation you plants need, in my opinion.

-Dave


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## ericpop27

I had lots of flow in the tank from powerheads and all, it seemed to annoy my plants more than anything. The fish loved it though, very much.

If turnover is the same question as "How many times should the tank volume be cleaned in an hour?" Then I would go with ten. I just upgraded my filter and it's at 10 times an hour now, the water is so clear I may drink it. There is still a lot of movement, even surface turbulence, but that's what really happens in nature.


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## houseofcards

I really don't think you need flow in the sense that you see the water actually moving that much. In most of our tanks that are 2 to 4 feet big, how much flow do you need to move dissolved ferts and co2 around. If your talking about algae control, I haven't seen any proof that algae grows more in areas with less flow. I've seen algae on people's tank right inside the co2 diffusor and right inside their return tubes. I have to believe there is flow there. Look at a pond outside. How much algae grows right on the rocks in a waterfall. There isn't one answer. It depends on your maintenance habits and other variables. Hobby why does Barr recommend alot of flow? By the way in terms of biological filtration this is a direct quote from Eheim:

_"EHEIM filters concentrate in biological filtration. If the flow is too hi, the water will not have enough contact time with the bacteria, therefore you will not have optimum biological filtration"._


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## chagovatoloco

This is a very interesting topic. I just moved my spray bar out of my tank to stop disturbing plants. When I read takashi amano's book I remeber how he said. " success is the awareness of things other people take for granted". And on his tanks he just seems to have one filter. But I have in the past seen that water flow can help control algae and keep things clear. I also respect every thing tom barr has to say and if he is promoting water movement I'm sure there is more to it than what I think. I would like to see some hard core facts on the issue. One my 29 gallon I have a fluval 205, so my tank cycles about 4 times per hour. I some times wish I had gotten a little bigger filter.


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## klaus777

QUOTE=houseofcards;407432]I really don't think you need flow in the sense that you see the water actually moving that much. In most of our tanks that are 2 to 4 feet big, how much flow do you need to move dissolved ferts and co2 around. If your talking about algae control, I haven't seen any proof that algae grows more in areas with less flow. I've seen algae on people's tank right inside the co2 diffusor and right inside their return tubes. I have to believe there is flow there. Look at a pond outside. How much algae grows right on the rocks in a waterfall. There isn't one answer. It depends on your maintenance habits and other variables. Hobby why does Barr recommend alot of flow? By the way in terms of biological filtration this is a direct quote from Eheim:

Hi Houseofcards, I have one comment to make regarding why you see algae forming on the inside walls of plumbing in filter tubing that that is a phenomenon called "wall drag" or "fluid slip". Where as in a pipe there are two flow rates actually occurring. One is in the centre of the pipe which is what we all see and preceive as the only flow. The other is caused by the "wall drag" this link my describe it better than I can;

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=14761

essentially what happens is on the inside of the pipes or tubes there are microscopic grooves where water traveling on the outside of the diameter of the water column get trapped in these grooves. The water that is on the inside track simply just slides over top the trapped water. Thus creating a wonderful little home for algae grow.
I personally believe that flow is required in an aquarium no matter what the nature of it (fish only, planted, or reef). The same basic principals or envolved, and that is we want to remove debris and toxic wastes from the inhabitants.
On the other hand too much direct flow could work against the aquarium environment where the plants cannot "catch" their food from the water column. So that leaves us with a nice gentle dispersed flow throughout the tank via a spray bar or multiple water return lines in order to get the job done. That's not too say that it is an absolute must have, after all if it works for some to have very little flow than that's all that really matters.

I hope this as shed a little light onto the subject.

Cheers to all!


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## houseofcards

Klaus777 that actually makes alot of sense and if that is true I think further illustrates my point. That algae will grow in high flow areas. These microscopic pores would also exist on wood, rock, hardscape and slow growing plants making increased flow useless in terms of algae control. The eheim statement about flow and biological filtration as well the statement you sourced :

_"On the other hand too much direct flow could work against the aquarium environment where the plants cannot "catch" their food from the water column. So that leaves us with a nice gentle dispersed flow throughout the tank via a spray bar or multiple water return lines in order to get the job done. That's not too say that it is an absolute must have, after all if it works for some to have very little flow than that's all that really matters" makes the case that too much flow can be an issue in certain situations.'_

Don't get me wrong, I believe in flow, I just can't imagine how much you need in a glass box 2 to 4 feet big.


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## OhioPlantedtankguy

ya know i dont know in a FW tank but in a SW tank you aim for at least 40 times per hour turnover.eep:


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## houseofcards

OhioPlantedtankguy said:


> ya know i dont know in a FW tank but in a SW tank you aim for at least 40 times per hour turnover.eep:


Flow in SW is completely different. There are many species of animals in SW that simply can't live without flow.


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## klaus777

I personally haven't read anything that has any theories on the amount of flow in a planted tank. All I know is the only turnover I have in my tank is from my filter which gives 8.57 turns per hour. It is a HOB so the flow is dispersed but really only gives enough flow for what I like on one side of the tank. In Duzzy's case he wants to use a sump so the question of flow wouldn't really matter since the return pump is going to dictate what the flow rate is, which will be also completely adjustable by plumbing a "dump gate" off the return line back into the sump. And if multiple return lines or spray bars this would greatly reduce target flow areas.


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## hoppycalif

The flow at the surface of all leaves is essential zero. Those surfaces are in a boundary layer, where the flow velocity is zero (ideally). So, leaves have no problem "catching" their nutrients. That very thin layer of water that is in contact with the leaf surface very quickly runs out of nutrients, giving a gradient of nutrient concentation tht goes from near zero at the leaf surface to average tank water concentration not too far away. We depend on the circulation in the tank to quickly replace the partially depleted water near the leaf with more water that does have nutrients in it.

Flow isn't what stops algae. We all probably see algae growing very well on our spraybars and other high flow hardscape elements. What stops the algae is the rapidly growing plants in the tank, which use up ammonia as soon as it is supplied by fish poop. But, without good water circulation the leaves don't get supplied with that ammonia immediately, and the leaves don't get a good continuous supply of the basic nutrients they need to grow rapidly.

Again, good flow isn't a half inch diameter high velocity blast of water. It is continuous water movement at a much slower velocity all over the tank.

I'm willing to bet that one year from now, there will be a different consensus about what is the best flow in a planted tank. In this hobby virtually none of our "rules" stay the same longer than a year. It's almost like chasing your tail.


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## chagovatoloco

Well put Hoppy, I have seen many rules change and seen beginners struggle with old books and abandoned ideas. It would be nice to have some hard core evidence on this.


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## houseofcards

Of course some flow is needed, I just don't think you need that much to have plants grow. And I'm sure there's quite a wide acceptable range in terms of plant growth, bio-filtration, etc., depending on one's setup. BTW how do the plants in a filterless nano setup grow. Is the flow that is created once a week during a WC enough? If flow is needed then that must be enough to provide them with nutrients. Or is it the small fish or shrimp swiming around enough to move nutrient rich water over the leaves. Either way the plants are surviving with almost no flow and certainly not flow on a regular basis.


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## BryceM

One thing that deserves some attention is to supply enough flow to keep detritus suspended in the water column. If you can do that, the canister filter will be able to remove it. If the gunk settles to the bottom, it's stuck there forever until you do a gravel vac.

One thing I've really noticed recently is the need to keep debris off of the plants. Algae have a hard time forming on healthy, quickly growing plants. They'll quickly set up shop on a small mass of rotting leaves or on a clump of stray debris.


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## hoppycalif

houseofcards said:


> Of course some flow is needed, I just don't think you need that much to have plants grow. And I'm sure there's quite a wide acceptable range in terms of plant growth, bio-filtration, etc., depending on one's setup. BTW how do the plants in a filterless nano setup grow. Is the flow that is created once a week during a WC enough? If flow is needed then that must be enough to provide them with nutrients. Or is it the small fish or shrimp swiming around enough to move nutrient rich water over the leaves. Either way the plants are surviving with almost no flow and certainly not flow on a regular basis.


Growing aquatic plants doesn't require a fixed, immutable set of conditions, or else the plants all die over night. I am a good example of someone who can grow plants under far from ideal conditions. You can grow plants with just fish poop as fertilizer, with no filtration, with low light, with algae all over the place, etc. What we are trying to do is grow them well, healthy and vigorous. That is what requires the good conditions, including good water circulation. As I see it, the real dispute is over what constitutes good water circulation. That issue is still up in the air. But, the trend seems to be towards a lot more circulation than we used to see in planted tanks.

We went through something similar with light intensity. We kept learning that we needed a lot more light than we were used to. So, people kept adding more light. Eventually we reached the point where we were using more light than we needed and causing as many problems as we were preventing. Perhaps water circulation will follow that path too.


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## duzzy

Hi all and thanks, hoppy calf would one inflow pipe get that movement?


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## davemonkey

Wisely spoken, Hoppy.


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## duzzy

Thanks all, I don't know what to do.....I was just going to have a slow flow through so the loss of co2 is minimal and on the return have an inline co2 diffuser and a one way ball valve to stop flooding in case of power outages. If water movement is the key I dont really know how to best achieve it


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## davemonkey

Duzzy, water movement is only one of the keys. We got a bit sidetracked from your original concern:

To reduce CO2 loss, you want to reduce surface ripple. Have your spraybar set at an angle that only barely ripples the surface. Don't worry so much about how many times your water volume is turning over. If you see detritus setttling on leaves or other surfaces in your tank, then you should re-evaluate circulation.

-Dave


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## houseofcards

hoppycalif said:


> Growing aquatic plants doesn't require a fixed, immutable set of conditions, or else the plants all die over night. I am a good example of someone who can grow plants under far from ideal conditions. You can grow plants with just fish poop as fertilizer, with no filtration, with low light, with algae all over the place, etc. What we are trying to do is grow them well, healthy and vigorous. That is what requires the good conditions, including good water circulation. As I see it, the real dispute is over what constitutes good water circulation. That issue is still up in the air. But, the trend seems to be towards a lot more circulation than we used to see in planted tanks.
> 
> We went through something similar with light intensity. We kept learning that we needed a lot more light than we were used to. So, people kept adding more light. Eventually we reached the point where we were using more light than we needed and causing as many problems as we were preventing. Perhaps water circulation will follow that path too.


Hoppy at this stage of the game for me I could clearly say based on my own personal experience that high flow is not necessary to grow healthy aquatic plants in an algae free environment long term. It really depends on alot of conditions, but the point I'm making is higher flow is not an absolute. I've kept filterless nano tanks long-term with no algae and very healthy plants. So other than stirring in some dry ferts with a spoon and having a shrimp crawl around the plants grow healthy for a year with no algae issues. So I would have to assume they arent' getting much in terms of flow. That's not to say that there could be a case where higher flow might help someone, but it still hard for me to comprehend that you need anything more than alittle movement to move ferts and dissolved co2 around two to four feet of water.


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## chagovatoloco

I remember when air stones where all the water movement we had. The tanks where clear and some grew plants, thought not as well as know. I would just like to add that an adequate co2 diffuser will move water as well. And as some one stated water changes with a gravel vac will also stop build up. I have chased the water flow dragon for algae problems, but I never found it to be and answer. though my opinion on this does change often, I think some controlled experiments are in order. Any volunteers?


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## klaus777

one thing I think we could possibly agree on is that, first off, aquatic plants are collected for different regions from all over the world each of which has grown and evolved in the conditions available, ie lakes, rivers and bogs. Therefore every plants threshold for not only the flow of water around it but also light intensity, iron levels, ph levels and so on and so on, are geared for the environment. With that being said these things are what is considered when re-creating those bio-topes in our tanks. I don't think it's fair to say that it is simply black or white for the flow. I do like the idea of a controlled experiment though, seems that would be the only way to really find out for sure.


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## duzzy

Thanks all, 

I think I will get a pump suitable for say 6 times the tank volume and see how that goes. I will say that I do not plan on using a spray bar I think they look woeful. I also am unsure if I should split the return in 2 or just keep the 1. Man every answers seems to give me more questions lol thanks all

Regards Darren


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## hoppycalif

houseofcards said:


> Hoppy at this stage of the game for me I could clearly say based on my own personal experience that high flow is not necessary to grow healthy aquatic plants in an algae free environment long term. It really depends on alot of conditions, but the point I'm making is higher flow is not an absolute. I've kept filterless nano tanks long-term with no algae and very healthy plants. So other than stirring in some dry ferts with a spoon and having a shrimp crawl around the plants grow healthy for a year with no algae issues. So I would have to assume they arent' getting much in terms of flow. That's not to say that there could be a case where higher flow might help someone, but *it still hard for me to comprehend that you need anything more than alittle movement to move ferts and dissolved co2 around two to four feet of water.*


Today I picked up a little more information. I was, along with a couple of other guys, helping Tom Barr move a 120 gallon tank into his house and we were talking about CO2 a little. He knows I have been puzzling over the need for so much water circulation. He mentioned that he had used his expensive CO2 meter to measure the ppm of CO2 in his 180 gallon tank, and asked me to guess what the results were. This tank has very good water circulation compared to anything I have had, with big Aquaclear filters and a big pump driving them, plus dual filter outlets and inlets in the tank. The results he got were: about 120 ppm near the filter outlet where the enriched water enters, about 40 ppm near the middle area of the tank, and 10 - 20 ppm down near the bottom in the middle of a bunch of plants. You have to admit that is astonishing. He has only cardinal tetras and some pencil fish in there - small fish. None were bothered by the CO2. (He is quite sure that larger fish would have been very much bothered by those levels.) And, even with the great circulation he had, the gradient in CO2 concentration was way beyond what he expected. So, he now has a big modified powerhead, with the model boat propeller modification, at one end, adding a whole lot more circulation.

The obvious question is how much did that help. But, the CO2 meter is out on loan to someone now, so he doesn't know yet. I'm still convinced that water circulation is an area where there is a whole lot more to learn. One thing I learned from this is that the CO2 we inject doesn't just come out of solution at the water surface, the plants are consuming large quantities of it. That should be obvious, but I hadn't really thought of it that way.


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## houseofcards

Well I did say *2 to 4 feet*. LOL.

My question is how are the plants doing on the far end of the tank where the co2 ppm was lower? Is there any difference between the ones near the return? I could tell you I have a 4ft tank with an eheim ecco and it effectively turns over the water once per hour. There is a spray on the left piece of glass angled down 45 degrees with a ceramic diffusor right below it. So the co2 goes up, hits the spray bar and is pushed left to right across the tank. There are two main rotala rountifolia groupings. One right near the spray bar and one on the far side side and their is no difference in appearance between the two groups either in fullness, color and pearling activiity. The testing might open a whole bunch of interesting information. I certainly will not doubt any of the readings from the tests taken, but one needs to just look at the plants to see what is necessary. And whether the co2 ppm is 100 near the return and 10 near the opposite side if the plants are growing great it tells me I don't need additional circulation and/or maybe we don't need 30ppm co2 as well. I don't believe any parameter works in a vacuum including circulation.


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## hoppycalif

houseofcards said:


> Well I did say *2 to 4 feet*. LOL.
> 
> My question is how are the plants doing on the far end of the tank where the co2 ppm was lower? Is there any difference between the ones near the return? I could tell you I have a 4ft tank with an eheim ecco and it effectively turns over the water once per hour. There is a spray on the left piece of glass angled down 45 degrees with a ceramic diffusor right below it. So the co2 goes up, hits the spray bar and is pushed left to right across the tank. There are two main rotala rountifolia groupings. One right near the spray bar and one on the far side side and their is no difference in appearance between the two groups either in fullness, color and pearling activiity. The testing might open a whole bunch of interesting information. I certainly will not doubt any of the readings from the tests taken, but one needs to just look at the plants to see what is necessary. And whether the co2 ppm is 100 near the return and 10 near the opposite side if the plants are growing great it tells me I don't need additional circulation and/or maybe we don't need 30ppm co2 as well. I don't believe any parameter works in a vacuum including circulation.


I agree. As usual, all of his tanks looked very good. He had a several day power outage while away, so he lost some plants and fish from that, and is still cleaning up the tanks, but they looked great to me, all over. Some day it will be possible for someone to say with confidence that we need at least X ppm of CO2 for the plants to do their best, but I don't think we are near that yet.

One thing to consider - if the CO2 is being consumed fast enough by the plants to lessen the concentration that much, the other nutrients must be depleted about as fast. So, circulation also acts to replenish them, too. But, I can't deny that whatever conditions he had, his tanks look great.


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## houseofcards

_One thing to consider - if the CO2 is being consumed fast enough by the plants to lessen the concentration that much, the other nutrients must be depleted about as fast. So, circulation also acts to replenish them, too. But, I can't deny that whatever conditions he had, his tanks look great._

Brings up alot of interesting points. Is circulation more important in a high light/tech tank if things are depleting faster? Do plants react to their environment based on flow and other variables and store things they need to continue to grow. If you consider a filterless nano tank that might get semi-weekly wate changes and the plants grow great. Are the water changes enough to move things around and get the plants what they need until the next water change, etc.


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## davemonkey

I'll volunteer to do a test, but it won't be as scientific as what might be desired (because I do not do water tests and don't own any test kits). But I could tell you if I notice any differences from what is currently going on in the aquarium.

Right now I've got an emperor400 HOB filter (it's got the bio-wheel on it) on the left-middle of my tank ( 50 gal, 48x12x18 ) . I've got a powerhead on the right/back corner (set on an UnderGravelFilter) set at an angle to assist in circulation to get water from the right-side to the emperor.

I can turn off the HOB and run only the powerhead (which doubles as my DIY CO2 reactor). That would cut off the majority of my water movement since the emperor pumps about 350 gph (is that right? It's rated at 400, but with filter cartridges....) and the powerhead only about 95gph. With the density of plants I have, circulation would be all but stopped on the left half of the tank. I'd essentially go from 9x per hour of turn-over to 2x with heavily reduced circulation.

Would this be worth doing without having the test-kit results to provide hard data?

-Dave

BTW, lighting is 2x65watt PC 6700/10000K; plus 2x15watt "Aquarium Bulbs" (came with original hood) that light the shaded spots in the foreground.


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## chagovatoloco

What I was thinking of was 2 tanks with identical setups, the only variable would be water movement. It is nice for your to offer your setup but think this may have other things affecting this as well. You have a biological filter built up in that wheel. Your tank is accustom to having that ammonium uptake with out it you will have excess ammonium, causing an algae bloom. aka green water, I have done this. By the way If you have co2 and a bio wheel the wheel is spitting out the co2 as fast as you are putting it in. My be your could turn off the power head and see what that does.


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## hoppycalif

http://www.barrreport.com/co2-aquat...eal-time-data-localized-co2-ppm-readings.html is Tom's own report on his CO2 measurements, for those interested.

I admit that I have no ideas at all about how to measure the effect of water circulation. It is easy to try increasing the circulation and see what happens, but if the plants grow better, you lose some of that increased circulation, canceling out the effect. You can also reduce water circulation and see what happens, but who wants to risk an algae outbreak? The idea of 2 otherwise identical tanks, one with a powerhead, preferably a Koralia, adding a lot more circulation, seems to be the best experiment that is possible for one of us to do.


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## davemonkey

Yes, I suppose I'd be pretty miffed at myself if wound up with tons of algae all over the place after shutting down my main fliter just for kicks.
Well, that rules me out of conducting the test. My "Financial Manager" (the Mrs.) would never let me get away with buying another tank (or two)...well, not anytime soon.


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## chagovatoloco

davemonkey said:


> Yes, I suppose I'd be pretty miffed at myself if wound up with tons of algae all over the place after shutting down my main fliter just for kicks.
> Well, that rules me out of conducting the test. My "Financial Manager" (the Mrs.) would never let me get away with buying another tank (or two)...well, not anytime soon.


Vary nice of you to offer your tank. I am in the same position as you, my "Financial Manager" wouldn't let me do that either.


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## Tex Gal

hoppycalif said:


> http://www.barrreport.com/co2-aquat...eal-time-data-localized-co2-ppm-readings.html is Tom's own report on his CO2 measurements, for those interested.
> 
> I admit that I have no ideas at all about how to measure the effect of water circulation. It is easy to try increasing the circulation and see what happens, but if the plants grow better, you lose some of that increased circulation, canceling out the effect. You can also reduce water circulation and see what happens, but who wants to risk an algae outbreak? The idea of 2 otherwise identical tanks, one with a powerhead, preferably a Koralia, adding a lot more circulation, seems to be the best experiment that is possible for one of us to do.


I continue to find this discussion very interesting. I have been reading Tom Barr's thread as well. It seems hard to imagine with that much flow that he has such a variance in CO2 measurements, but you can't argue with the facts. The next question is why? Can some plants actually take up the CO2 so fast that he'd get such fluctuations? Then I ask, so how do we overcome the fluctuations if at 18X turnover he still has such fluctuations? Do we plumb our tanks so that the CO2 enriched water is released every 25-30 cms around our tanks? It will be interesting to see if there is any resolution....


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## duzzy

Well my financial manager has just said I can get a 4x2x2 what ya reckon should I ask for a second one lol

thanks all for the info there seems to not be a firm answer on this as of yet.

So now the question is. If I have my 4x2x2 with its weir/overflow in the center. And face 1 return to the left and one to the right creating two semi circles of water flow and back to the weiw would that be ok? and on the returns I have something like this


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## hoppycalif

I use a filter return like the one in that photo, and I really like it. It creates good water flow, but doesn't blast the water into the tank so fast it tears up the plants and substrate. Your two outlet plan sounds good, but a lot will depend on how dense the plants get, and how much they block the flow.


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## duzzy

Thats a point I had not considered hoppy, I think with 2 there should be enough flow.


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## fshfanatic

duzzy said:


> Hi there,
> 
> I was wondering how many time should the tank volume turnover in a heavily planted tank turn over? and when calculating this do i include the sump volume as well as the tank volume?
> 
> Regards Darren


Are you talking filtration rate or water circulation rate? These can be two different things.

I am a huge advocate of over filtration and keeping the current in the tank enough to make sure that no debris can settle on the substrate.

For instance, my 29 gallon planted RCS tank is being filtered by an Eheim 2215 which creates enough flow so as no debris can settle on the SMS I am using as substrate. The tank is very heavily planted and the shrimp seem to love it along with my Ottos.

You should try to balance the filter flow and the circulation rate. Too much circulation and not enough filtration rate can cause the debris to just constantly float around in your tank, so you will have to take into consideration the tank as well. What are the dimensions? Is it a tall tank, long tank, etc.


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## duzzy

Hi there, 

the tank is 4x2x2 but I am still decided where to put the weir and returns for be circulation


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## nfrank

*Hydor Koralia -- which model for large tanks?*

I am thinking about adding one or two hydor koralia to increase flow in middle/bottom of a tank.... to better disperse CO2 and other nutrients. Tank sizes are 90 and 120g, each with 2 returns at the top. I would probably place them along back wall near corner.
To those who have used HKs, would you like to have larger or smaller models than you currently have? Also, do you suggest two small models in ea tank, say two no. 1 (400gph), or one larger no. 3 (850gph)? Are there any quirks about these models to point out?
thanks, Neil


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## essabee

Till this date I have got away with very little circulation in my planted tanks. They are very high lit tanks (using direct sunlight + supplemented with 3WPG), well planted with good community fish population, and using a lot of CO2 (bubble counter showing 1 pea size bubble every 3mm in a free vertical rise for my 240G) and only 2 power-head pumps for my UGF each having a max capacity of 800 L/H (which I doubt is achievable after the resistance of the UGF, the in-line reactors, and the home-made spray-bars). The flow is imperceptible, though well distributed; but keeps the water reasonable clear. There are no other enhancer of flow in the tanks.


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