CO2 and EI

[Martin in Holland]

I found that getting the CO2 right is the most difficult part in our hobby, because CO2 is not just pump it into your tank and voila....it also has to do with flow/ distribution, plant mass and more. I pumped in as much CO2 as the fish could handle and went little by little down until the plants started to show signs that they needed more...upped a bit and now I'm fine (I think )

 

[Christos Ioannou]

I have just added a pressurised CO2 system to my tank for the first time and am running it at 2 BPS but the Drop checker will not go green ( I'm scared I will kill the fish if i get this wrong). I am using Ei dozing for the plant fertiliser which is all so new to me.

For what's it is worth, the BPS in my bubble counter are beyond counting, on a tank of similar size (55" x 15" x 13"), to achieve a pH drop of 1 unit before lights come on. (co2 is on 2hrs before lights come on, and goes off 1 hr before lights go off) as far as a ph automatic controller is concerned, I suppose that this may result in fluctuating co2, which will bring algae in your setup. I am also using an inline co2 atomizer and a powerhead for better circulation. Fish, shrimp seem to be just fine.

From a fellow newbie, good luck.

 

[the.tech.guy]

Thanks all for your in put, I was thinking that same about the PH Controller so i think i will give it a miss for now.

 

[ian_m]

am running it at 2 BPS but the Drop checker will not go green

I would suggest you have a leak somewhere. I have less than 2bps with JBL bubble counter and in my 180l tank drop checker is like this anywhere in the tank.

Before I located all the leaks in my CO2 system I had quite high bubble rate and drop checker barely moving off blue. Dunk all the CO2 (except FE of course) in to a bucket of water and wiggle the tubes and find all your leaks. I am using an inline diffuser on filter outlet.

 

[X3NiTH]

The other way to use a controller to regulate the co2 in a tank is to control how the gas escapes the tank. You can use this UP pH controller from co2Art to control an air supply to off gas co2 rather than close the solenoid on the co2 and have the system depressurise. I have a Weipro controller also, if this is used to control the co2 solenoid there will be a fluctuation of 0.2pH around the desired set point. Using the UP in LO mode to control off-gassing rates via an Airstone there is a fluctuation of 0.1pH, the crucial difference is the co2 never gets switched off and continues to come into the tank at the same injection rate. Blowing the extra gas off is quicker than depressurising the system and waiting for the gas to leave the tank naturally.

You still have to Nanny a controller because they don't learn the pH fluctuation in the tank due to biological influences or EI dosing. It's a good way to prevent untimely fish deaths (providing you have it all configured right) due to too much co2.

 

[plantbrain]

I assume that if you pump too much CO2 into your (critter-free) tank, then your pH could drop too much. If you have a pH aboud 6, then most of the nitrifying bacteria go dormant. At pH around 5 most of the bacteria (not only the nitrifying ones) are not working anymore. That's potential risk for planted tank. Also, if you reach some extreme level, then the high concentration begin to work against plants ... I mean, too much CO2 could prevent further growth and cause destruction (the same apply for other nutrients and light also).
It's always better to keep your parameters in some reasonable range.

pH drop has nothing to do with it, respiration of heterotrophes do. Bacteria, inverts, fish etc.
If you have a high ppm of CO2 and the O2 stays the same, then it'll be harder and harder to respire.
I'd assume that it also the care for plants since they respire also, but after say 50-70 ppm of CO2, there's not much point.

You gain nothing by adding more than that, 35 ppm is not the overall limit.
35 ppm MIGHT be for a tank full of Anubias with say 40 umol of light.
But likely will not be with a tank full of touchy stem plants with 120umols of light.

Likewise, adding full EI to a tank with sediment ferts, low light, slower growing plants, might be larding it on................while another high light stem tank might perfect.
EI is just a non limiting start point.

You can treat CO2 the SAME way, but CO2 is much more toxic than the ferts.
And people mess it up more than fertilizers.

Light is pretty stable.
So adjusting the light, not the ferts, often helps a lot if you have trouble with CO2.

Still, CO2 management is the biggest problem for new and even old planted hobbyists.

 

[Marcel G]

35 ppm is not the overall limit.
35 ppm MIGHT be for a tank full of Anubias with say 40 umol of light.
But likely will not be with a tank full of touchy stem plants with 120umols of light.

I have a tank right now where I have 100-120 µmol PAR at the substrate, and about 400 µmol PAR at the water surface. And my CO2 concentration (according to the dropchecker) is somewhere around 15-20 mg/L CO2. The O2 level in my tank is somewhere around 80 and 115% of O2 saturation level (see picture) → 80% at night, and 110-115% during photoperiod.

Here's a picture of this tank:

Do I have any algae problems? No.
Do I need to use EI in there? No.
Do I have any nutrient deficiencies? No.
Do I need more then 20 mg/L CO2 to have a nice algae-free high-light planted tank? No.
Do I need to bother with CO2 management (the same way EI users do)? No.

 

[Martin in Holland]

S

I have a tank right now where I have 100-120 µmol PAR at the substrate, and about 400 µmol PAR at the water surface. And my CO2 concentration (according to the dropchecker) is somewhere around 15-20 mg/L CO2. The O2 level in my tank is somewhere around 80 and 115% of O2 saturation level (see picture) → 80% at night, and 110-115% during photoperiod.

Here's a picture of this tank:

Do I have any algae problems? No.
Do I need to use EI in there? No.
Do I have any nutrient deficiencies? No.
Do I need more then 20 mg/L CO2 to have a nice algae-free high-light planted tank? No.
Do I need to bother with CO2 management (the same way EI users do)? No.

So you are saying that when using EI my CO2 will be more in demand?

 

[Marcel G]

No, I'm saying that 15-20 mg/L CO2 may be sufficient for a good growth of even the most demanding plants under very strong light. There's absolutely no point IMO to head for 50-70 mg/L. I'm not a plant seller, so I don't need to have a tons of biomass each week in my tank. If you use EI and lot of CO2, then your plants will grow like crazy, and you'll enter into the realms of big problems with good CO2 management (as one of my friend noted). Any mistake with CO2, and you end up with a lot of algae and bad plant growth. So with EI you got rid of nutrient deficiency problems, but immediately you end up with much worse problems of good CO2 management (which is according to Tom Barr the most tricky thing to set correctly).

I keep lower CO2 levels, and lower nutrient levels, and even under strong light I have no problems with algae or bad plant growth. And if I want some growth boost, then I increase PO4 dosage a little, and in just one week all my stem plants are reaching the water surface (with the same CO2 level of 15-20 mg/L under 100 µmol PAR at the substrate). I really see no point in pumping tons of nutrients, and tons of CO2 in there, to produce tons of biomass each week ... and to get into serious troubles with good CO2 management.

 

[parotet]

Absolutely agree with this. I'm not sure 100% which is the physiological mechanism behind all this but in my mid light (70-80 micromol PAR) tank with good co2, see my ph drop below, dropchecker yellowish, etc. I never get rid of BBA in the old leaves or difficult areas of the tank (to the eyes of everyone it is a free algae tank, but not for a planted tank hobbyist)

http://www.ukaps.org/forum/threads/new-setup-from-2-to-just-plants.34374/page-2

IMO, EI recommended levels for PO4 (at least the ones in this site or Barr's site) boosts plants' growth very significantly, and once this nutrient is not limited anymore, CO2 is again the most limiting or at least the most difficult parameter to meet... Probably to high biomass to be fed? To more difficult flow due to the biomass growth? not really sure, but it seems that good CO2 is more difficult to achieve and BBA appear.

I have noticed significant changes just using an EI method with lower PO4... Let's say adding 1 ppm instead of 3-5 ppm of PO4. My previous light and my previous CO2 (according to ph drop should be around 30-40 ppm) is now perfect and the tank looks nearly algae free.

Ok, once we are here (nothing new for most of you I'm sure), the answers would be:

- 'that is because you have too much light'. And my reply would be that reducing light is the key points of course, but not only for EI but for all the planted tanks methods. The fact is that now my light is the same and co2 demand is more feasible

- 'EI never said to use fix values, just decrease the amounts use until you notice side effects'... Ok, so we are not in that method of unlimited amounts, we are getting close to other approaches, such as PPS-Pro. Anyway, I don't care which name or brand the method has, but if we have to decrease to adjust the system, IMO the method lose part of its point

- 'you need more co2'. I think I am not a newbie on this. I've been fine tuning my setup for two years, my estimations of CO2 (I don't own a co2 meter) all seem to point in the right direction. It also amazes me how high co2 has to be in most of the high light EI tanks... Because CO2 is by far the most difficult issue in a planted tank. So a method that was intended to be for the newbie (no test, no accuracy in dosing...) ends up with super demanding co2 levels (agree that mostly when playing with high light)

- 'you blame PO4 and it is demonstrated that PO4 is not responsible for Algae'. And I totally agree. It is not PO4 to be blamed, umy guess is that PO4 high levels drives to very demanding CO2 levels which are very difficult to achieve. Therefore PO4 do not create algae but creates an scenario in which BBA can easily appear.

Of course I may be wrong in some of the assumptions I made and I would be very happy if someone can point out why I am wrong.

Jordi

 

[pepedopolous]

OK Parotet,

Can you quantify your mix of PO4 in teaspoons? I used 4 teaspoons of KNO3 and 1 teaspoon of KH2PO4 in 500ml of water. Then when I got some problems with GSA/GDA on my Staurogyne I increased the KH2PO4 to 2 teaspoons and I haven't stopped using this mix even though the GSA/GDA has gone.

However, BBA is always coming back regardless of flow, CO2 or light.

Thanks,

P

 

[Martin in Holland]

Maybe Tom Barr can elaborate on this, after all he is the EI guy.

 

[parotet]

OK Parotet,
Can you quantify your mix of PO4 in teaspoons? I used 4 teaspoons of KNO3 and 1 teaspoon of KH2PO4 in 500ml of water. Then when I got some problems with GSA/GDA on my Staurogyne I increased the KH2PO4 to 2 teaspoons and I haven't stopped using this mix even though the GSA/GDA has gone.
However, BBA is always coming back regardless of flow, CO2 or light.
Thanks,
P

Hi, someone did this work in UKAPS some long ago...
http://www.ukaps.org/forum/threads/teaspoons-to-grams-conversion-via-chemical-density.33331/

4 tsp of KNO3 = 42 g
2 tsp of KH2PO4 = 23.4 g

Using any of the available nutrient calculators and introducing the volume of your tank and you will see what are you dosing to the water column... but it seems quite a lot of KH2PO4 to me. Anyway, I'd give the floor to someone else with more experience and knowledge so we can have good and reliable advice on my "probably not that good theory about high PO4 driving to more demanding CO2 and more chances of BBA".

I increased the KH2PO4 to 2 teaspoons and I haven't stopped using this mix even though the GSA/GDA has gone.

As mentioned by Marcel (aka ardjuna) in another thread about nutrients' plant consumption, dosing high levels of nitrates and phosphates (I mean not just an excess but a large excess) can have cross-cutting benefits beyond plants' nutrition, which is fighting against blue diatoms or GSA (these algae don't like high levels of these nutrients... have you ever had blue Green diatoms... just sprinkle some nitrates over and gone). Or as suggested in this thread, maybe very high CO2 levels can also help to prevent algae... when I reduced the PO4 EI standard dose (3-5 ppm, closer to 5 ppm; then went to 1-2 ppm) in my tank I did it very slowly to be aware of the effects and... yes these algae appeared but nothing to be worried about.

Jordi

 

[Marcel G]

Weekly nutrient consumption according to my two tests (I do other tests also to verify these data, but they are not finished yet):
Tank #1: 62L → 3 g CO2, 3 mg/L NO3, 0.2 mg/L PO4, 0.6 mg/L K, 0.001 mg/L Fe → 100-120 µmol PAR at the substrate
Tank #2: 112L → 6 g CO2, 4 mg/L NO3, 0.2 mg/L PO4, 0.7 mg/L K, 0.001 mg/L Fe → 70-100 µmol PAR at the substrate
Both tanks are high-tech ones. By raw estimate I add to the first tank around 4.7 g CO2 per day (just during the photoperiod), which is ~33 g CO2 per week. At that time my dropchecker was lime-green (~35 mg/L CO2). In the first tank I fertilized sporadically (still I did not saw any nutrient deficiencies in there). In the second tank the fertilizing regime was as follows: 7 mg/L NO3, 6 mg/L K, 0.8 mg/L PO4, 0.8 mg/L Fe (weekly).

From the above results of my tests I would say that CO2 is somewhere close to the saturation point in most tanks. So when we maintain 35 mg/L CO2, we may have 10-times more than our plants really need (in most setups). So even if we would have ~10-15 mg/L CO2, still this should give us nearly the same results (in "normal" densely planted high-light tanks with a strong light of 100 µmol PAR at the bottom). Also, I think that most of us add much more than 3 mg/L NO3, 0.6 mg/L K, 0.2 mg/L PO4, and 0.001 mg/L Fe into our tanks. In the second test we added 0.8 mg/L PO4 weekly, so if you add 3 mg/L PO4 each week, then your plants will probably grow even more ... but the percentage difference should not be high. But do we really want our plants to grow like crazy? Is there anyone (except the ones who sell plants) who wants his plants to grow like crazy? Is there anyone who revels in trimming his plants each week?

In water, the uptake of CO2 is limited by slow diffusion. Although we can raise CO2 concentration in our tank, our aquatic plants are still limited by slow gaseous diffusion. High CO2 levels in the planted aquarium allow the plants to use less nitrogen for Rubisco. So, if less enzyme is needed because the CO2 concentration is high, the proteins can be used in other processes in the plants leading to formation of new biomass. So at higher CO2 level, less nutrients are needed.

According to the study of Andersen & Pedersen, at 250 µmol PAR and 7 mg/L CO2 the growth rate (= increase of plant biomass) is approx. the same as at 90 µmol PAR and 40 mg/L CO2. Also the difference between 250 µmol PAR and 40 mg/L vs. 250 µmol PAR and 7 mg/L (or vs. 90 µmol PAR and 40 mg/L) is only 40% in plant biomass. So if we have a strong light (250 µmol PAR), and then we raise our CO2 concentration from 7 mg/L to 40 mg/L, we gain only 40% of plant biomass (i.e. our plants will grow only by 40% more).

 

[pepedopolous]

Hi guys,

EI can mean NO3 concentrations of anything from 5-30ppm and PO4 concentrations of 1.0 to 3.0ppm.

According to the nutrient calculators, the EI recipe I use (from aquariumplantfood.co.uk) gives 5.10ppm NO3 and 1.56ppm PO4.

With such a wide range of concentrations for NO3 in particular, can I be sure that I have 'unlimited' NO3?

Also what on earth do people mean when they say they dose 2*EI? This could be anything from 10 to 60ppm NO3 I suppose, but 10-30ppm is in the range of normal EI!

P

 

[Martin in Holland]

Weekly nutrient consumption according to my two tests (I do other tests also to verify these data, but they are not finished yet):
Tank #1: 62L → 3 g CO2, 3 mg/L NO3, 0.2 mg/L PO4, 0.6 mg/L K, 0.001 mg/L Fe → 100-120 µmol PAR at the substrate
Tank #2: 112L → 6 g CO2, 4 mg/L NO3, 0.2 mg/L PO4, 0.7 mg/L K, 0.001 mg/L Fe → 70-100 µmol PAR at the substrate
Both tanks are high-tech ones. By raw estimate I add to the first tank around 4.7 g CO2 per day (just during the photoperiod), which is ~33 g CO2 per week. At that time my dropchecker was lime-green (~35 mg/L CO2). In the first tank I fertilized sporadically (still I did not saw any nutrient deficiencies in there). In the second tank the fertilizing regime was as follows: 7 mg/L NO3, 6 mg/L K, 0.8 mg/L PO4, 0.8 mg/L Fe (weekly).

From the above results of my tests I would say that CO2 is somewhere close to the saturation point in most tanks. So when we maintain 35 mg/L CO2, we may have 10-times more than our plants really need (in most setups). So even if we would have ~10-15 mg/L CO2, still this should give us nearly the same results (in "normal" densely planted high-light tanks with a strong light of 100 µmol PAR at the bottom). Also, I think that most of us add much more than 3 mg/L NO3, 0.6 mg/L K, 0.2 mg/L PO4, and 0.001 mg/L Fe into our tanks. In the second test we added 0.8 mg/L PO4 weekly, so if you add 3 mg/L PO4 each week, then your plants will probably grow even more ... but the percentage difference should not be high. But do we really want our plants to grow like crazy? Is there anyone (except the ones who sell plants) who wants his plants to grow like crazy? Is there anyone who revels in trimming his plants each week?

In water, the uptake of CO2 is limited by slow diffusion. Although we can raise CO2 concentration in our tank, our aquatic plants are still limited by slow gaseous diffusion. High CO2 levels in the planted aquarium allow the plants to use less nitrogen for Rubisco. So, if less enzyme is needed because the CO2 concentration is high, the proteins can be used in other processes in the plants leading to formation of new biomass. So at higher CO2 level, less nutrients are needed.

According to the study of Andersen & Pedersen, at 250 µmol PAR and 7 mg/L CO2 the growth rate (= increase of plant biomass) is approx. the same as at 90 µmol PAR and 40 mg/L CO2. Also the difference between 250 µmol PAR and 40 mg/L vs. 250 µmol PAR and 7 mg/L (or vs. 90 µmol PAR and 40 mg/L) is only 40% in plant biomass. So if we have a strong light (250 µmol PAR), and then we raise our CO2 concentration from 7 mg/L to 40 mg/L, we gain only 40% of plant biomass (i.e. our plants will grow only by 40% more).

Shouldn't you also mention which kind of substrate you are using in those tests? ADA amazonia for instance is high in nutrients, as are many more or maybe you even added some tabs to your substrate....and so on ....
Anyway, I just did a 4 day black out in my BBA invested 40 liter tank which I used the EI method and will now try to use Tetra Flora Pride (3ml every other week) inject CO2 with pressure bottle, the substrate is a small grain gravel only without any nutrients added.

 

[Marcel G]

The values I stated above are not what I added to the tanks (actually I added much more than that), but what plants used up.

 

[Marcel G]

Look at this article: "Comparison of the photosynthetic characteristics of three submersed aquatic plants". This article is a key to understanding how much CO2 aquatic plants are able to use up. Let me summarize it a little:
The study discusses three aquatic plants (weeds) and their photosynthetic rates at non-limiting light and CO2 levels.
According to this study these aquatic plants have the following half saturation levels of CO2 (Km):
1) Hydrilla verticillata: 170 µM = 7.48 ppm (at pH 4), 90 µM = 3.96 ppm (at pH 8)
2) Myriophyllum spicatum: 150 µM = 6.60 ppm (at pH 4), 75 µM = 3.30 ppm (at pH 8)
3) Ceratophyllum demersum: 165 µM = 7.26 ppm (at pH 4), 95 µM = 4.18 ppm (at pH 8)
The 100% saturation level of CO2 is 0.5 mM = 22 ppm (0.5 * 44 g/mol).
These values applies for a temperature of 30°C, and light intensity of 1000 µmol PAR !!!
The authors say, that the above half saturation levels of CO2 (Km) "probably represent close to the maximum rates attainable by these three species at 30 C, and as far as can be ascertained, they are the highest rates reported for submersed aquatic flowering plants".

So, what does it mean? "Half saturation level" of CO2 means such a conditions where plants have 50% of the maximum CO2 which they are able to use up under ideal conditions. If you add more then this, your plants will actually grow more, but not that much. I would say that at this half saturation level of CO2, plants reach about 70-80% (authors say "close to the maximum rates") of the maximum growth rate. So these plants can grow at ~70% of their potencial with as low CO2 concentration as 4-7 ppm! And the maximum level they are able to utilize is 22 ppm CO2.

Beware: These are extremes (at 30°C, 1000 µmol PAR, and with aquatic weeds), and not averages (25°C, 100 µmol PAR, and variety of different low- and high-light aquatic plants) !!!

So again my question: Is there any need or reason for us to aim for more then 10-20 ppm of CO2 to have a good growth?

The paradox is that even T.Barr in his main EI article on Barr Report says that:
"The maximum CO2 level no matter what light set up you might have is about 30ppm* for these three very fast growing weeds, which we can assume have higher CO2 needs/demand than slower growing aquarium plants subjected to less intense lighting than sunlight."
*He made a mistake in converting mM to ppm (it should be 22 ppm).

 

[Marcel G]

EI can mean NO3 concentrations of anything from 5-30ppm and PO4 concentrations of 1.0 to 3.0ppm ... With such a wide range of concentrations for NO3 in particular, can I be sure that I have 'unlimited' NO3? ... Also what on earth do people mean when they say they dose 2*EI? This could be anything from 10 to 60ppm NO3 I suppose, but 10-30ppm is in the range of normal EI!

This question should be answered by the author of EI method (Tom Barr) in the first place. But if he says that some (unspecified) plants can consume up to 30 ppm of NO3 per week*, and you (of course) don't know if it's your case (i.e. if you have these plants in your tank), then I suppose you should aim for the higher end of the range ... to be safe. That's (I think) the reason why people say that EI means 30 ppm NO3, 3 ppm PO4 ... etc. So when some people say they use 2xEI, it means that they are just extremists who have no idea of what can mean "unlimiting".

*PS: Have a look at post #27, where there is a picture of my densely planted tank with unlimiting CO2 levels (~20 mg/L) and strong light (100 µmol PAR at the bottom) with a weekly consumption rate of about 3 ppm of NO3.

 

[parotet]

Marcel, I wonder if such high injection levels we have in our tanks are needed to meet these uptake quantities mentioned in your post. Maybe we need to inject twice or three times the plants can uptake because our diffusion efficiency is low (i.e. We need to ripple the surface in order to reach stable levels and we know this degasses the water column)

Jordi

Edit: good distribution of co2 in all the tank can be another good reason to add much more gas than the plants need?