CO2 MEASUREMENT USING A DROP CHECKER

[plantbrain]

My tap KH varies from 6 to 13 so everytime I complete a WC I have to reset the DC. This involves alot of effort in tweaking and monitoring and by the time you've got it sorted, it's time for another WC. Imo this makes DC impractical. At one end of the scale your in real danger of killing your fish and the other, inducing algae.

Since EI is a proponent of the "no test kit" methodology, I often wonder how many other people have the same problem and aren't even aware of it.

Well, EI says nothing about test or not to test CO2, nor light.

I'm no fan of the DC's, but I also do not fall for pH controllers for the same reasons with KH changes and influences on that parameter. pH meter at least have a much much higher accuracy concerning pH measure, DC's have 3 different measures basically.

In the past, we used pH meter(not controllers) and set it at the assumed pH/KH combo. From there, we'd adjust the pH down slowly and methodically, setting it another 0.05pH units and then watch and observe fish, plants, algae. After 2-3 weeks, we might adjust it down a tad more till we see nice lush growth and no algae.

You can also do this with a needle valve, turn the valve say 1/20th more CO2 gas and watch each time.

By doing this slow and step wise, you hit a nice CO2 sweet spot and can tell what subtle changes look like and thus...can respond appropriately in the future. This is much more valuable than mere feast or famine CO2 dosing.

This same slow adjustment can be applied to EI as well, starting at the higher non limiting level downward and then bump back up to the next highest level once you find a negative effect due to limitation. No test kits for either.
Lighting is a one time typical test and then that's it/done.

So it depends on how you approach it, no testing is not really the goal, we use plants, fish, algae as test kits in all cases(they are much more specific to our goals than ppm's etc really).

Regards,
Tom Barr







In both cases, no test kit is really needed.

 

[plantbrain]

BTW, since we can rule out nutrients and measure light and adjust appropriately, this leaves mostly CO2 as the main variable for growth and issues.

Clive suggest using plants, algae and indirectly fish(I'm not a fan of usign them) as the "CO2 test kit".
This is mostly what I have done, then once set to an optimal range, I go back and then I test CO2........


This way I have a known reference to compare the CO2 or NO3 or light etc to...........if you have algae, issues, something is not right, it might be the testing method etc. How many folks have a known CO2 reference solution that they can measure and compare accurately like we do for N3 or light even?

Say a known 5ppm and a known 50ppm CO2 stock solution?

Not many, I'll tell you that, so calibrating CO2 test methods is not easy.
We can calibrate pH/KH/NO3 etc..........but CO2 is much harder. Without knowing CO2 well, any issues with nutrients are impossible to isolate well.

There are issues with DC's, pH/KH etc, and thermo couples. Each have trade offs, but the slow incremental adjustments and watch and wait is also a good method. Skill and observation are required to do it though.

I'd suggest more focus there, some get luck and dial ina good CO2 using DC's or pH/KH, or bubble rates or eyeballing it. Many do not however and helping CO2 become more consistent is a good goal.

Regards,
Tom Barr

 

[sWozzAres]

Thanks guys this helps somewhat. The other issue that hasn't been mentioned is timing, specifically hitting the point of minimum pH/maximum CO2 (for bpm) at some point during the lighting phase, course this is messed up with variable KH since it takes longer/shorter depending on KH change.

Talking of using fish as a test kit, my fish really aren't happy just prior to the lights coming on, lots of co2 and little o2. 2 gasps a second is concerning for fish that gasp once every few seconds during normal "operation". So I got an air stone today to get more o2 in the water sometime between 6-9am. Lighting phase is 3-10pm with co2 on 2 hours prior to this. Of course using an air stone throws things out of sync even more (co2 escape) making timing yet another thing to "worry" about!

Regards...

 

[giwight]

Hi All,

Great article and thread.

Is the JBL Drop Checker featured in this article still available, if so does anyone have a link as I can't find it with Google.


Regards
George

 

[bogwood]

Try this supplier.
http://www.aquaessentials.co.uk/jbl-per ... -p-77.html

Also most Maidenhead Aquatic stores carry a good range of JBL products.

 

[giwight]

Hi Bogwood,

Thanks for the link, I don't know how I missed it.

Regards
George

 

[ceg4048]

Thanks guys this helps somewhat. The other issue that hasn't been mentioned is timing, specifically hitting the point of minimum pH/maximum CO2 (for bpm) at some point during the lighting phase, course this is messed up with variable KH since it takes longer/shorter depending on KH change.

Talking of using fish as a test kit, my fish really aren't happy just prior to the lights coming on, lots of co2 and little o2. 2 gasps a second is concerning for fish that gasp once every few seconds during normal "operation". So I got an air stone today to get more o2 in the water sometime between 6-9am. Lighting phase is 3-10pm with co2 on 2 hours prior to this. Of course using an air stone throws things out of sync even more (co2 escape) making timing yet another thing to "worry" about!

You know, one of the things I find laughable is when people refer to an CO2 enriched tank as "high tech". Nothing could be further from the truth. The way in which we measure CO2 and the way in which we inject it is so Stone Age that it could only have been conceived by Fred Flintstone. Once the needle valve is set, the injection rate is constant, so the CO2 concentration builds to a peak level over time. The rate of concentration rise is mediated by the CO2 loss due to evaporation (the major factor) + uptake of the plants. The injection rate needs to be high enough to overcome the loss but not so high that it builds to toxic levels. That's really a very tricky balancing act.

It is for this reason that pH controllers became popular. In a perfect world, the controller would open the throttle and drive the CO2 concentration to the desired level. Once this is achieved the throttle can then be reduced to maintain this level. The problem of course is that the controller measures a corrupt reading of the pH because it's measuring tank water. As the non-Carbonic related acids rise and fall, and as the alkalinity varies due to kH, this fools the pH probe. There are ways around this, but I'm waiting for the day that someone incorporates a (low cost) proper CO2 meter which can determine the CO2 levels within minutes instead of hours, which can be used instead of a pH meter. Then we'll have a proper high tech CO2 controller.

For now, the best we can do is to turn the gas on much earlier than we need to, say 2 hours before lights on. In this way the peak equilibrium concentration can be reached just at lights on, after which time evaporation + plant uptake will keep the levels from rising. Then you can turn the solenoid off a few hours before lights off. It's not necessary to run the gas until exactly lights off. The critical time for CO2 is at lights on and the first few hours thereafter. This is when tanks are made or broken. It's OK if the concentration starts to fall in the second half of the photoperiod. In this way, if you turn the gas off much earlier, you lower the concentration during the dark and early morning periods and thereby reduce the stress on the fauna.


Cheers,

 

[rob_s]

Just a quick question, is their a way to control co2 using ph and solenoid.
I do understand that there are other reagents in the water affecting acidity so a direct check is not possible, however, I was wondering if you are able to use a factor to control.....for a rough example:

1) run tank without co2 until ph stabalises.
2) run tank with co2 using drop checker to get required ppm of co2. take , PH measurement
3) set c02 selanoid to ph measurement recorded in step 2

currently i have 160x30x30 tank, 116 litres with amazonia 2 aquasoil.
tap water is soft Kh 2-4, ph is 8
filter is large Ehiem, so enough water changes
after running the tank the PH currently stabalises at 5.5, with KH 2
fish are south american acidic, soft water, eg cardinal neon, rummy nosed tetra etc.
I am worried about the effects of Co2 on the acidity. I know you metioned not to worry as the acidity is a reflection of the overall conditions, not the specific toxins themselves, however as the ph is already 5.5 I don't want to lower it further. I am unsure of the effect of co2 will have if is start to add to the soft water. if the co2 gives a ph of 4 when added to distilled water, it cannot reduce PH below 4 when added to the tank and as the acidity aproaches 4 will have less and less an effect, is this correct?

comments greatfully appreciated,

cheers

Rob

 

[ceg4048]

Hi Rob,
I guess it's not really clear to me what the nature of your reservations are about adding CO2 to soft water. I've kept cardinals and rummy nose tetras in soft water pH 3 or so with added CO2. My dwarf chiclids bred in the community tank under these conditions.

I also think people don't really understand what pH is and this might be the root of their fear. pH simply means percent Hydrogen. It can be thought of simply as a ratio of the amount of Hydrogen ions (H+) in the water compared to the amount of Hydroxide (OH) ions. pH actually tells you nothing about the amount of Hydrogen, only the ratio. Carbon Dioxide reacts with water to produce a very weak acid called Carbonic Acid. It's considered a very weak acid, because it does not result in a lot of H+ being dumped into the water. A strong acid like Muriatic acid or Sulfuric Acid cause massive quantities of H+ and this is highly toxic. But the percentages, or ratios of H+ to OH- when any of these acids are added to the water are very similar. So that a pH of 3 due to Carbonic acid or Vinegar (Acetic acid) or Lemon juice (Citric acid) is not toxic but a pH of 3 due to Sulfuric acid can be lethal.

So people really need to get over pH numbers and try to understand what these parameters actually mean. Otherwise we become paralyzed by things that are meaningless. I can positively guarantee you that the strong acids used in products like "pH Down" are actually highly toxic even if they are added to high KH water and only result in a minor drop in pH, because the damage is being done by the quantity of Hydrogen ions, not by the ratio. The large ph drop caused by CO2 in soft water is meaningless because very little H+ is released into the water.

The amount of CO2 that is added to the water by injection is completely independent of the starting value of the waters pH. This is another fundamental principle we need to remember. Whatever buble rate you use on your KH 2 water will have exactly the same effect as if the water were KH 12 and had a higher starting pH value.

If you still insist on keeping to some desired pH limit, then all you have to do is to add some form of bicarbonate to the water. Potassium Bicarbonate or Sodium Bicarbonate can be added which will raise the KH and thereby buffer the carbonic acid, which will prevent the ph from dropping below your desired limit.

Hope this clarifies.

Cheers,

 

[rob_s]

thanks ceg,
I am now starting to add co2 as per your comments re PH 3. My fear was due to most books like bede atlas which give a range of PH for different fish.

The only thing I am still thinking, is it would be good, if possible, to utilise the ph meter and solonoid I already have to indirectly measure and control co2 in tank. this would save me having to faff with replenishing dye in drop checker once a week etc. I've had another idea (other than the steps 1,2,3 in my previous post)..... would it be possible to put the sensor probe of the ph meter into the drop checker. the ph could then be set to open / close co2 using the standard tables?

I'm guessing you're comments are going to be to use the dye checker and bubble counter in the first few weeks to monitor and adjust bubble counter until a steadystate of desired co2 is reached, after which only random checks should be required?

thanks again for your comments and help

 

[ceg4048]

Hi Rob,
Yes, over the years, we've collected enough data to see that typically, a pH drop of about 1 unit from the starting water pH value correlates well to a workable CO2 concentration level. That means that before you start adding CO2 (blue dropchecker), if you measure the pH of the tank water to be say, 5, then if you add CO2 and measure the pH a few hours later, a pH of about 4 will typically indicate that you have a good injection rate. If the pH drops significantly more during the day then this will indicate that your injection rate is too high. Again, this does not mean that you will cause damage to fish as a result of too low pH. What it means is that you will do damage to fish due to too much CO2. Remember, to avoid misunderstanding, that I do not know your starting tank water pH value. I'm just using these numbers as an example. I'm not saying that you should have necessarily have a target pH of 3. So if your starting pH before adding any CO2 is 4 then yes, a target of 3 should be accompanied by a lime green or slightly yellow dropchecker.

The dropchecker is just a simple "quick reference guide" to give you an idea of how things are generally progressing.

Once you have seen that you have good growth, no CO2 related algae and a lime green dropchecker then you can confirm what the pH value is of the tank water and use that as the set point for the controller. pH controllers are notorious for causing CO2 instability (and resultant BBA) because they turn the gas on and off in order to control the pH. So I prefer not to use them and to only use their monitoring function, but once you have figure out how to trick them by finding the right set point and right gas working pressures, you can use them effectively. I always discourage their use for beginners because of the subtleties we're discussing now. Once you understand that neither fish nor plant care about pH or pH fluctuations, and once you understand the role of CO2 then you can use any tool or measurement at your disposal.

It's absolutely a bad idea to try and put the probe in the dropchecker water because the dropchekers response time is several hours. Review the article. It states specifically that the dropchecker only only tell you what the CO2 concentration was a few hours ago. Only a dedicated CO2 meter can give you real time data on CO2 concentration in water. CO2 meters cost thousands of pounds.

When collectors go out to find fish for later sale to the hobby, they often measure the pH of the lake or stream that they caught the fish in or collected the plant from. The range of pH that they measure then becomes the de-facto published pH range for that species, yet, the fish and plants do fine in other pH ranges. It's only when we are trying to spawn that the water parameters have to be paid attention to because the parameters are often used by the fish to trigger spawning behaviour. There is no need to rigidly adhere to any pH value outside of this context because that causes more problems than it solves.

Cheers,

 

[rob_s]

Thanks for the information Ceg,
It's really interesting and helpful.
I have now started running the co2 at one drop per sec, lighting time only and monitoring the PH (for reference / callibration only)
fish look fine, (no surface swimming / lethergy /disorientation)
PH has dropped from around 5.8 down to arround 5.3
PH rises at night about 0.3 (5.3 to 5.6)
the plants are fizzing very slightly.
All seems well therefore, and I will monitor for next couple of weeks and if all well, I will up the co2
I will also hopefully buy a drop checker this weekend. (I live in Dubai, and this type of equipment is quite difficult to find).
If not I will buy on my next trip overseas.

Thanks again and cheers

Rob

 

[rob_s]

Hi Ceg,
Another question I am afraid.....
I managed to get a jbl drop checker which is pretty amazing given the stuff thats normally on sale here, I bought the only two infact left in the shop.
Problem is I can't find KH4 or dionized water.
I am thinking to use some Sera PH 7.0 ph meter calibration liquid I have with added bicarbonate of soda.
I cannot get the calibration liquid here, so i need to use it reasonably frugrally
I checked web and cannot determine the hardness of the calibration liquid or if it is dionised.
I'm not a chemist, and any advice you can offer on the sensativity of the hardness or if the water needs to be dionised would be greatly received. eg if it turns out the sera liquid has hardness of 0 can I use without bi-carbonate soda?

cheers

Rob

 

[rob_s]

Hi Ceg,
a very quick update,
I tested the hardness of the sera PH 7.0 calibration liquid and the reading is off the scale. the liquid is very, very hard.
The tap water I have here is soft KH 3-4 and PH 8.0 (it's desalinated). Can I use this if I check hardness and PH prior to use? I know it's not dioinised?

cheers

Rob

 

[ceg4048]

Hi Rob,
No, if it's not distilled/de-ionized then it's not a good idea to use it in the dropchecker. You can make your own if you have access to an RO unit.

Cheers,

 

[sWozzAres]

how long does the DC fluid last? I am careful with mine, it stays under the water during WC and I try to disturb it as little as possible so I am thinking that the fluid might last forever!! Although I suspect this isn't the case.

 

[ceg4048]

Well, there is no published life for Bromo Blue, and as long as the color changes continue then it's OK. We just recommend to replace it every few weeks or so just from a cleanliness perspective.

Cheers,

 

[jalexst]

Hey Ceg,

Glad this thread has been bumped to the top, I've not spotted it before...

I have just read through the posts and have a few questions, apologies if I have missed the answers posted already...

So. Key points are:

Turn on CO2 a couple of hours (or so) before photoperiod begins to reach optimum ppm at "lights on." At this point you put:

...after which time evaporation + plant uptake will keep the levels from rising. Then you can turn the solenoid off a few hours before lights off. It's not necessary to run the gas until exactly lights off.

Untill recently I was under the impression that the dropchecker would need to reach blue again, so that when lights are off, the co2 produced by plants would'nt harm the fish. But since the DC is telling us what happened a couple of hours ago, that wouldn't be accurate to see. Is the primary reason for cutting CO2 early, simply because the plants don't need it at this time?

Also. I have read in another post of yours that the maximum lenght of time photosynthesis occurs is preditermined by the plants. So. lets say 8 or 9 hours is the max (not sure if it is) and that is the lenght of the photoperiod. Does that mean that the CO2 demand is at its highest at "lights on" and is Steadily dropping off throughout the photoperiod? And if so what does that mean for those of us with a shorter photoperiod? (mine is 5 hours purely to save dosh.) What I mean is, am I cutting CO2 too early, 3.5 hours into the photoperiod?

At the moment I have seen the first signs of BBA and am trying to perfect the CO2 injection. What is a feasable timescale to observe changes? If I tweak the CO2 one day, can I observe the difference it has made in week 1 or 2 weeks after for example?

and on that thought how detrimental is it if CO2 suddenly runs out? If there are a couple of days between cylinder refills, will It be a major blow to the tank, and if so what can I do in the meantime? (buy another cylinder probably)

Again, my apologies if these queries have already been addressed.

Thanks Ceg,

Jack

 

[ceg4048]

...Untill recently I was under the impression that the dropchecker would need to reach blue again, so that when lights are off, the co2 produced by plants would'nt harm the fish. But since the DC is telling us what happened a couple of hours ago, that wouldn't be accurate to see. Is the primary reason for cutting CO2 early, simply because the plants don't need it at this time?

Hi Jack,
Yes mate, it's as simple as that. Many aquatic plants have the ability to collect and store CO2 so that later in the photoperiod they have built up enough reserves to carry on even with a drop in available CO2. In the morning though the coffers are empty and it's difficult for them to get everything running smoothly. A crude analogy would be sort of like warming your car motor up on a cold day. You need a little bit more fuel until things warm up.

At night, there is no Oxygen production, and the plants are actually competing with fish to breathe Oxygen. At the same time, both plants and animals are expelling CO2 into the water, which all adds to the residual levels of CO2 that built up during the gas injection time. By morning, Oxygen is low. To make things worse, Oxygen does not dissolve in water nearly as much as CO2 does, so at some point in the early morning you have a worse case scenario for fish. Even so, it is not a requirement for the DC to be blue, and in fact, if the DC is blue in the morning then it make it more difficult to get enough CO2 into the water in time for when the plants need it. The fish are able to adjust to the CO2 levels. As long as the concentration at night is lower than it was during the peak period, the fish will be given a break from the stress. Turning the gas off earlier allows an earlier respite for the fish while not significantly affecting the plants ability to photosynthesize in the second half of the photoperiod.

Also. I have read in another post of yours that the maximum lenght of time photosynthesis occurs is preditermined by the plants. So. lets say 8 or 9 hours is the max (not sure if it is) and that is the lenght of the photoperiod. Does that mean that the CO2 demand is at its highest at "lights on" and is Steadily dropping off throughout the photoperiod? And if so what does that mean for those of us with a shorter photoperiod? (mine is 5 hours purely to save dosh.) What I mean is, am I cutting CO2 too early, 3.5 hours into the photoperiod?

Well, it may mean a lot or not that much, depending on the other things that you are doing;
Of course it means that the plants only produce food for 5 hours instead of 8-9 hours, so they won't gain weight as much as if they were producing food for 8-9 hours, but so this is not really a big deal.
It also means that the CO2 will fall to lower levels, since the gas off time will be longer. The implication here is that you need to pay more attention to get the gas concentration levels up to optimum levels by lights on as you are bringing the concentration up from a lower value than someone who has the gas on for a longer period of time. But the same rule applies here - lime green DC at lights on. This means you may require a higher injection rate, or may need to turn the gas on earlier than others to get your lime green color by lights on.

At the moment I have seen the first signs of BBA and am trying to perfect the CO2 injection. What is a feasable timescale to observe changes? If I tweak the CO2 one day, can I observe the difference it has made in week 1 or 2 weeks after for example?

The thing you've got to remember about BBA is that BBA loves CO2 just as much as plants do, so you cannot just tweak CO2 and always expect to see BBA disappear. You actually have to eradicate the BBA in order to "clean the slate". If the BBA does not reappear, only then will you have known that the tweak actually worked. Sorry, but both CO2 and BBA are very complicated issues. So I would suggest that you tweak, then prune, then dose or overdose Liquid carbon until the BBA turns pink, then stop the liquid carbon and see if the BBA returns. If it returns then you need to tweak again.

..and on that thought how detrimental is it if CO2 suddenly runs out? If there are a couple of days between cylinder refills, will It be a major blow to the tank, and if so what can I do in the meantime? (buy another cylinder probably)

Good Heavens, it's Mega-detrimental. Yes it's a major blow - a blow to the solar plexus, which can result in an 8-count, and which might even cause the referee to stop the fight with algae the winner by TKO. Turn all lights off immediately until you have the bottle refilled mate.

Cheers,

 

[jalexst]

Great help as always,

Thanks Ceg.

Just reading back through my post from last night and noticed I veered quite heavily off topic!

One last thing, you mentioned...

Of course it means that the plants only produce food for 5 hours instead of 8-9 hours, so they won't gain weight as much as if they were producing food for 8-9 hours, but so this is not really a big deal.
It also means that the CO2 will fall to lower levels, since the gas off time will be longer.

Wait. I thought in the lights off period that many factors are involved in producing CO2... so I always had a fear that during the super long lights off period CO2 levels would rise and rise, and I would awake to see all my fish floating! (hence the "running DC down to blue" half-theory) So I take it from what to are saying that the CO2 production is not that great during lights off (in comparison to injecting at lights on)? and that the CO2 still is falling even though it is being produced at the same time? I think I remember in another post of yours that you mentioned the production of oxygen being somewhat independant of the production of CO2. So are they happening at the same time, just one outweighing the other?

Thanks again,

Jack