Limited affect of CO2 In Hard Water ?

[Blueskiesdz]

I'm tapping into your infinite knowledge please as I've probably received incorrect advice from my local fish shop.

I've read and learned from this site for weeks before setting the tank up but the chap in the shop who's very confident has confused me some what !

Recently set up 36x18x18, 2 HO T5, Eheim Prof 350 and running CO2. I've recently planted it out with Tropica soil and I've noticed it takes an age (3 hrs +) for the CO2 drop checker to turn green (4 bps). The return is one end of the tank in a central position and the atomiser is low down in the opposite end.

The chap in the fish shop told me the checker will struggle to reach the optimal level as the water is so hard in Leicesteshire and I should be using RO water.

I personally think the checker is not going green due to poor water movement with only one source of movement maybe ? I really don't want to be using RO water again after years of using it in my reef tank which is now gone ! I was hoping just to use tap water via a mixer tap set at the right temperature and adding dechlorinator. Obviously I'll take advise and act accordingly if I'm asking for trouble.

I've tested the ph in my tank and its 7 and 7.4 from the tap. I'm unsure the KH though. A silly question but will the KH change the more days c02 is injected into it ?

Please someone give me the RIGHT advise.

 

[Manuel Arias]

Hi Blueskiesdz,

Well, several points from your comments:

-Lack of movement in the water: It is unlikely with the filter you have. Water mixing is not going to be the problem. The CO2 diffusor, however, it can have impact if generates too big bubbles, reducing the efficiency of your CO2 injection.
-Hardness in the water: It can be a problem. pH is not enough information to see this, as pH is affected by many factors and components in the water. You have to check kH to know where your levels of carbonates is.

The kH plays a main role in the amount of CO2 soluble in water in addition to the pH, so you have to control both to understand what is going on in your aquarium. Additionally, the temperature in the tank will also have a role into this. Note that the solubility of gases in water highly depends on the temperature, but in the usual scales this has a minor impact than the relationship between pH and kH. However, if you have 28ºC for example, it will be easily a significant variation respect to the solubility you get at 25ºC.

For instance, you can find some ideas about this, in the tables representing this relationship and the maximum solubility of CO2 in the water:

Example here: http://www.theaquariumwiki.com/images/d/da/CO2_Graph.gif

So, in essence, if you have a pH of 7.2-7.4 and a high dkH, what is happening you is that your levels of CO2 are not high enough to trigger the change of colour in your indicator. However, it is not meaning that you have no the right levels of CO2. So, I would recommend to use this sort of table and measurements of kH and pH to see where are your maximums, in addition to the information of the indicator.

Other option is to check the water you use in the indicator. Usually, the CO2 indicators work by creating a small chamber of air between the indicator mix and the water of the aquarium. That works as follows: The aire acts as a gas exchanger between both liquids, so the concentration of CO2 in the chamber will depend on the concentration of CO2 in the tank. On the other side, there is a communication of CO2 between the indicator liquid and the chamber too. However, as the relative volumes are very different (volume of the tank vs volume of indicator liquid) the concentration in the chamber will depend only of the concentration in the tank. Hence, the flow of CO2 to the indicator liquid is just related to this one, and then the pH of the mix , which is the triggering factor of the colour, it depends only of the composition of the water in the indicator mix and the CO2 levels in the tank. If you are using water from the tank to prepare your mix, and the water has a high kH, then you are buffering the mix, i.e. increasing the maximum solubility of CO2 and then, having difficulties to impact the pH and see the change. You can see this by temporarily changing the water in the indicator by RO water, or a mix of RO and water in the tank. Note that most of these commercial indicators are calibrated to work at a pH of 6.8-7.

And finally, just a short explanation of what is happening: CO2 dissolves in water becoming in great proportion into HCO3- by dissociating a molecule of water into a proton (H+) and an hydroxile ion (OH-) and taking the hydroxyle to become in HCO3-. The reaction frees a proton in the water, making it more acid, reason why the pH reduces when injecting CO2 in the tank. HCO3- can also release another proton and become in CO3(2-), but due to the CO3 not being very soluble, this reaction happens in much lower proportion than the solution of CO2 in the water. The levels of CO3(2-) and HCO3- are then also in equilibrium. This implies that when you increment your kH in the water (that shows you basically your levels of CO3(2-) in it) you are pushing the equilibrium towards the formation of HCO3(-) from the levels of CO3(2-). As this reverse reaction takes one proton from the water, it increases the pH. This is what is called a buffer effect. The impact of this consist on when you add CO2, you are increasing your HCO3(-) concentration, but the acidification caused by it is hidden by the buffer effect of the CO3(2-), which keeps stable your pH. As the pH does not change, or change just a little, then your indicator mix will no reflect the increments of CO2 in the water, and then you are forced to provide higher dosis of CO2 to force any change of pH in the water. That is why I think part of the problem can be with the indicator mix you use.

I hope this help.

Cheers,

 

[Tim Harrison]

Short answer - ignore the dude in the LFS. I've always lived in very hard water areas and had no problems.
It takes time to find the right balance, just keep playing with the CO a la Clive's tutorial http://www.ukaps.org/forum/threads/co2-measurement-using-a-drop-checker.467/ especially read the bit about Zeroing in on 30 ppm.
It can take that long to get the lime green but if there are no critters to gas it makes it easier to experiment and find the optimum.
And don't get fixated on the bubble rate it's pretty meaningless, it's just an abstract refernece for you to help zero the CO2 in...

 

[Blueskiesdz]

Manuel thank you so much for taking the time to write such a detailed response. If im honest some parts are way above me at this stage in the game ! I'm a little embarrassed after so many years reef keeping that I can be so much of a beginner again ! It's good to try something new which is why I'm here.

In relation to water movement I was under the impression that the plants in the tank need to be 'swaying in the breeze' ? The return is hitting the far side and there is plenty of movement but on the other side nearest the return very little. My indicator is over near the return and I purchased it and the solution. I also have checked th temperature and it was 27 so I've adjusted down to 25.

So if there is a high dkH then the co2 even at the correct flow will show an incorrect reading on the indicator ? So I suppose it would be quite feasible to keep increasing the co2 to get the right colour but in turn wiping out the fish etc in the tank ? In this situation would it be wise just to scrap the indicator and use a dkH and ph test kit and refer to the graph you kindly supplied ?


Troi thanks for your input mate much appreciated. With reef I know a reasonable amount so I don't generally listen to 'I heard it from a man down the pub' type advice. I'm just new to planted tanks and perhaps like in any situation when your looking for advice or open to advice people can give you their suggestions (which are definitely right!) As I said above to Manuel could I go overboard on the co2 just to get the green colour in the indicator ? The mist/fog from the atomiser also from co2 art is quite something and I'm unsure whether I should turn the co2 up anymore to get the right colour. This is why I mentioned flow as I presumed the fine bubbles needed to flow around the tank to get to all the plants.

Bear with me I'm learning

 

[Tim Harrison]

No worries...and so am I - still learning that is

So if there is a high dkH then the co2 even at the correct flow will show an incorrect reading on the indicator ? So I suppose it would be quite feasible to keep increasing the co2 to get the right colour but in turn wiping out the fish etc in the tank ? In this situation would it be wise just to scrap the indicator and use a dkH and ph test kit and refer to the graph you kindly supplied ?

A drop checker is a bit of a blunt instrument, just as most hobby grade test kits are...but the short answer to your question is no.
A drop checker filled with 4dkH solution is still the best way of measuring CO2 conc. there is very little chance of wiping out your critters if it's used correctly - if there were, none of us would be using them

If you're worried about your flow try pipetting some non-toxic coloured liquid in to the tank and take a look at the flow dynamics.
Not sure about the turnover of your filter but the standard is around 10x tank volume per hour. So if your tank is 100 litres the filter needs to turnover 1000l/h. However, its the flow that's important so if you're short you can always just add a powerhead.

 

[Manuel Arias]

Hi Blueskiesdz,

Well, yes. I tend to be too much technical, but I always believe that understanding the principia behind the things help a lot in doing the right things. I am glad that the answer could help you.

Regarding the question of the filter, this is quite easy to see. I assume you gave the dimensions of your tank in inches, so that goes for 183 litres tank, approximately. The Eheim professional 350 has a flow rate of 1050 l/h so the number of times per hour the whole volumen of the tank tank pass by the filter is around 6. ADA systems, that I do not believe we can complain about, have rates for that size of tank between 300 l/h for the 600 Series (up to 90x45x45cm tank) and 960/l for the 1200 Series (starting at 90x45x60cm tanks and up to 120x45x60cm), so clearly your rate is good enough. In fact, too much flow can cause mechanical stress to the plants, and not all the species will tolerate it well. As fishes, different plants will grow better under specific flow conditions, so I really doubt the rate you have is the problem in your CO2 levels. If you are not very happy in how the CO2 is dissolved and spread in the tank, you can go for a better diffusor, or even to an in-line injector, which usually optimizes the dissolution of the CO2 bubbles and also making them smaller.

So if there is a high dkH then the co2 even at the correct flow will show an incorrect reading on the indicator ? So I suppose it would be quite feasible to keep increasing the co2 to get the right colour but in turn wiping out the fish etc in the tank ? In this situation would it be wise just to scrap the indicator and use a dkH and ph test kit and refer to the graph you kindly supplied ?

A drop checker is a bit of a blunt instrument, just as most hobby grade test kits are...but the short answer to your question is no.
A drop checker filled with 4dkH solution is still the best way of measuring CO2 conc. there is very little chance of wiping out your critters if it's used correctly - if there were, none of us would be using them

And regarding the drop checker, the right answer is that works meanwhile you have some considerations. As mentioned by Troi, and also pointed out by me in the first answer I gave, the kH levels in the drop checker are rather important to make sure the readings in the checker are valid. If you have a high dkH in the drop checker, then you will face problems to get the right readings. As Tori proposes, you can made your own water for the drop checker and fix it to dkH of 4, which is a quite soft water, so definitively, if you have hard water in the tap, tap/aquarium water will not make a good solution, I think. And regarding your question, if the dkH in the drop checker is too high, then you could have the right levels of CO2 but not seeing it in the drop checker. As commented also before, the drop checkers only reacts to pH changes in the mix of water and indicator in the drop checker, so if you are buffering the mix by using hard water, then it will not give you the right readings.

Of course, this does not mean that the drop checker is useless, but I think that interpreting what it is telling is not just a matter of expecting the right colour. They get green colour only when the pH goes between 6.8-7 inside the drop checker mix. Over 7 you will find it blue, and below 6.8 you will find it yellow. For instance, if you pay attention to the table I put before, and imagine a dkH of 8, the amount of CO2 that has to dissolve to see impact in the drop checker is about 24 mg/l. However, with a dkH of 4, the amount of CO2 becoming green the indicator is of 12 mg/l. So you can see the impact of what I am saying. This is still safe for your plants ad fishes, but explains why you have to inject a lot more CO2 in the tank to get the right levels at high dkHs than a lower dkHs.

Cheers,

 

[MirandaB]

Great reply Manuel although I may need to read it a few times for all the tech stuff to sink in

 

[Manuel Arias]

Great reply Manuel although I may need to read it a few times for all the tech stuff to sink in

Thanks! Well, quite technical true be said. In any case, a thorough explanation is found in the link provided by Troi in this thread, if that heps, as there is also explained what I am saying in plain words, more or less. I can, however, provide any clarification if required, so ask me if needed.

Cheers,

 

[Blueskiesdz]

I've just completed a dkH and it 4 and the ph is 6.2. Looking at the above table it shows double the required levels ! The confusing part for me is that the drop checker is still showing a shade of blue !! The solution is from co2 Art and is new so I would not have thought that's the issue. My bubble counter must be 8 drops a seconds.

Which result would be the reliable reading ?

 

[alto]

Don't forget that the drop checker has a delayed response time of at least 30 min (some posters report an hour or more ... )

In terms of flow/distribution, you can play with positioning of the inlet & outlet

eg I have mine at opposite ends of the tank, I use a single spray bar (it came with the filter kit ) pointing the length of the tank so there's not a chance the stream will get anywhere near the opposite side of the tank ... but it fits nicely (& provides more even flow than alternate positions)

I have an Eheim Prof 250 on a similar sized tank (90cm x 45cm x 52 cm internal dimensions) & there is some movement of plants following the outflow from the spray bar, the C helferi planted near the intake has leaves flowing back in the direction of the spray bar so I can easily visualize the circular flow path (coincidence) ...
there isn't much visible current movement at the substrate level directly near the spray bar but I have the CO2 diffuser situated there & can visualize the microbubbles that rise ~ halfway, then are dispersed into the water column (none rise to the top of the tank in a direct path from the diffuser)
I have very soft water, kH 0-1, GH 1-2, acidic pH (except when the water board is playing with additions)) so I can gas my fish very easily - that bicarbonate equilibrium in water that Manuel is referring, in soft water, it's the dominant pH effect.

So your local fish shop chap is correct - in a practical sense, it's much easier to get desired CO2 levels in RO water
- but you'd also better stay on top of your nutrient dosing, as there's none otherwise, hence the recommendation to mix tap & RO water if you decide to go this route ... which I wouldn't!
In the end, there are always some plants that do better in soft or hard water, though most can be cultivated in either.

Check kH & GH of your water, also pH out of tap vs standing overnight, you can get a detailed water analysis through your water supplier - information is often online already.

 

[Blueskiesdz]

Hi Alto thanks for your reply.

So would I need to turn the co2 up even higher to get the drop checker green at the point the lights come on ? My confusion is the test kits results looking on the graph show double at that point. So the result in the checker was from an hr+ ago so I'm thinking I'd need to turn the co2 up even more to get it right at lights on.

My tap water ph is 7.6 and kh7.

I've also noticed some of the plants are yellowing which im guessing is from insufficient nutrients. Would high co2 cause any issues like this ? Also the crypts are melting but again from reading on ukaps this happens regularly I think ?

With regards to flow I have the return one side and the out flow the same side of the tank just opposite corner. The diffuser is at the far side low down where the water will be initially hitting after being filtered.

I just don't want to keep turning up the co2 un necessarily. At the moment there's no fish etc so no suffering.

 

[alto]

I've not looked at the specific linked graphs but by convention they are generated for systems in which bicarbonate in the dominant buffer with limited contribution from other buffering systems which may occur in water, hence my suggestion to check your local water analysis.

You can also try running lower levels of CO2 24/7, eg begin with 2bps & see how plants respond, you may still obtain best result by increasing CO2 to 4bps at 1-2h before lights come on, then reduce CO back to 2 bps 1-2 h before lights off ...
in other words, let your plants tell you what works best/better rather than going by chart/drop checker.

Do you have surface scum/film? this will greatly impact gas exchange with atmosphere (your source of oxygen dissolved in water, unless you have a venture device on your filter or a sump etc)

As to yellowing, how long has tank been set up, which plants etc, etc

Most plants are grown emerse, than adapt to submerse culture in tanks ... depending on various factors, the emerse leaves may remain intact for some time or show almost immediate "damage" (often related to shipping etc trauma rather than immediate response to your particular submerse conditions, also factored by leaf type/species).

Crypt melt is often just an indication of change in the environment (they melt in the wild too)

 

[Blueskiesdz]

The tank has been set up one week There is no surface scum as I have a surface skinner attached to my filter.

I'm unsure the type of plants but there's slight yellowing on most of them. I have the lights on for 5 hrs with the co2 coming on two hrs before. Would it be a good idea to reduce the co2 but increase the time it comes on before lights on ?

 

[alto]

I'd begin conservative

1) leave same CO2 levels surrounding your current light period

2) run reduced CO2 24/7 OR begin CO2 4 hours prior to lights & stop CO2 1 hour after lights (again this goes back to how much ambient light tank receives)
The CO2 schedule is about getting/maintaining sufficient dissolved CO2 in the water column during hours of plant respiration not just during hours of artificial light.

3) if you see consistent improvement over the next 1-2 weeks, then this may be the path to follow (or some version of it anyway)

Try to change 1 thing at a time, then wait.

At this point, we're focusing on CO2 levels & assuming they are insufficient.
You can try increasing CO2 flow into the tank, try adjusting CO2 dissolution into the water column, look at CO distribution in the water column (though if most plants in various areas of the tank show similar symptoms, distribution is an unlikely culprit)

How much growth are you seeing?
Again it's helpful if your plants are known identity - go back to seller & request id's
You can also post detailed photos & get some decent guesses here.

Some queries:
Tropica soil - powder or regular?
Tropica Growth Substrate?
Fertilizers?
Plant nursery?
Water change details?

 

[Blueskiesdz]

I'm using tropica soil and easylife profito ferts. Water change every 3 days approx 40% each time. Plants are mainly tropica but some from aqua flora and flora media. The ones which don't appear to be doing to well are -

Pogostemon helferi melting leaves

Microsorum pteropus trident yellowing

Juncus reopens leaves yellowing

Pogostemon erectus leaves turning black

Growth in most plants is good just some appear to be suffering with yellow and black patches and this is all around the tank. Lights on 5 hrs and there's not to much ambient light.

 

[alto]

I'm not familiar with this fertilizer range but did find this

ProFito does not contain nitrate or phosphate

This is unlikely an issue in the early stages when plants are mostly growing/adjusting from reserves but you may want to look at this later, some tap water contains sufficient N & P, heavy fish loads/feeding can supply N & P ...

Only the M pteropterus stands out on that list, it's usually a very sturdy plant, whereas similar observations for the others you mention is not uncommon.

Have you looked through Mark Evans journals - lots of excellent photographs in his journals, take note of the light levels, especially distance from the tank to the luminaire - it's quite possible that you are still CO2 deficient for the light levels, I'd not change your 5h photoperiod but would likely raise the lights (assuming they are fairly close to the tank surface) and increase CO2.
Once plants are established & there's little signs of algae, begin to back off on the CO2 gradually

Also remove damaged/melting leaves as they contribute little to plant health, most feel they act more as a drain on plant resources - certainly they affect the integrity of the plant's barriers to external environs.

Unfortunately there is no guaranteed RIGHT advice, only guesses based upon what you report, the more detail you're able to include, the more educated the guesses coming in ... photos are often very helpful in triggering more guesses & more insightful guesses

 

[Blueskiesdz]

Alto thank you as ever for taking the time to give me such great advice. The co2 is now spot on after I started the co2 3 hrs instead of 2 and turned it down to 3 drops a minute. I think now a week later the tank is starting to balance out a little bit more.

 

[ceg4048]

The kH plays a main role in the amount of CO2 soluble in water in addition to the pH

This is not true at all. There is no relationship between the KH or pH of a water sample and the solubility of CO2 in that water.
The solubility of CO2, or ANY gas is a function of pressure, temperature and to some extent, salinity. No other parameters or factors are relevant.

Short answer - ignore the dude in the LFS.

Words to live by.

Cheers,

 

[Manuel Arias]

This is not true at all. There is no relationship between the KH or pH of a water sample and the solubility of CO2 in that water.
The solubility of CO2, or ANY gas is a function of pressure, temperature and to some extent, salinity. No other parameters or factors are relevant.

Apologies for debating you all the time, but here, again, you are mistaken. In general the solution of gases, by physical laws, depends only, as you well said, pressure, temperature and some extent, salinity. However, this is only true under the point of view that the gas concentrations of water are not affected by external factors.
When you increment kH levels, you are incrementing carbonates levels, and I am sure we will agree into that. At the same time, carbonates act as a buffer element of the solution, hence, they have capability to capture protons from the water, avoiding the pH to change when adding an acid solution to the water. The carbonates then become in HCO3 when protons are released to water. On the other side, CO2 becomes in HCO3- when goes to solution, so the three species, CO2, HCO3- and CO3(2-) are in a chemical equilibrium that is triggered by the pH, as shown in the following figure:

As you can see, there is a relatinship between the chemical form of inorganic carbon and the pH, which also links to the kH, as this parameter represents the total content of carbonates. This mechanism can limit the pCO2 in water, as in fact, the reason why CO2 is so soluble in water is because becomes in HCO3- in most of the total flux of CO2, not being a gas anymore, and then allowing more flux of CO2 to the water until the point of saturation of HCO3-, and then starts the carbonates formation. This whole balance is controlled by pH. Hence, your assumption that CO2 only plays with the inert gas laws is not accurate. You can find some information about that here:

http://www.soest.hawaii.edu/oceanography/faculty/zeebe_files/Publications/ZeebeWolfEnclp07.pdf

And also explains why so many aquatic plants have adaptations to use HOC3- in addition of CO2, like the mechanism you explained some time ago:

http://www.ukaps.org/forum/threads/what-form-of-carbon-do-water-plants-use.26887/

And please, let me remark this: The only reason why we can increment the CO2 levels until such a point is because becomes in HCO3- which is no longer a gas, so leaves the games of the perfect and inert gas laws, allowing more injection.

 

[fablau]

The CO2 schedule is about getting/maintaining sufficient dissolved CO2 in the water column during hours of plant respiration not just during hours of artificial light.

Is that really true? For example, my lights turn on at 2pm, and my Co2 starts at 10am, but I have some ambient light around the tank between 7am and 10am... So, should I have my Co2 turn on at 6-7am??