# Spray Bar and CO2 Diffuser placement confusion



## MMonis (23 Mar 2021)

Hi,

I am going to rescape/restart a 54 litre aquarium and am planning on getting the necessary equipment before I start with the rescape.
Initially I was planning on getting steel lily pipes but felt that due to the jet type output, the flow may be too concentrated and I risk blowing off the carpet plants which I intend to establish.

After some research I thought of getting a Fluval Spray bar kit as it will fit well into my Fluval 106 cannister filter output. So no additional pipework/tubing changes or mods (to accomodate lily pipes). 
I have also had poor circulation in the tank with the existing Fluval standard outlet, so hoping that the spray bar will solve the issue and provide both good circulation and surface agitation.

Since the length of my aquarium is 60 cms, I will need to connect both bars (15 cms each) so that the entire tank length is covered for circulation.
I plan to rescape the tank with a triangular layout, consisting of plants, driftwood and carpet plants (Marsilea Hirsuta). I will have an in-tank CO2 diffuser and will also use the standard inlet pipe of the Fluval 106.
I am confused in terms of placement of the spray bar, CO2 diffuser and the filter inlet.

The image shows the equipments and where I think to place them.




1) If the CO2 diffuser is placed towards the front left of the glass, will the CO2 bubbles reach the right side (back and front) of the tank where I intend to grow the carpet ?
2) If the CO2 diffuser is placed at the rear of the tank, next to the filter inlet, will this effectively distribute CO2 throughout the tank ?
3) What would be the best placement of the 3 components i.e. spray bar, filter inlet and CO2 diffuser considering my scape layout ?

Regards,
Mel.


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## Libba (23 Mar 2021)

I was facing this issue recently and felt like I wasn't getting good distribution regardless of placement. My guess is that your best bet would be to have your diffuser in a position such that your filter inlet is sucking in most of the CO2.


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## MMonis (23 Mar 2021)

Libba said:


> I was facing this issue recently and felt like I wasn't getting good distribution regardless of placement. My guess is that your best bet would be to have your diffuser in a position such that your filter inlet is sucking in most of the CO2.


In this case if I place the diffuser at the rear of the tank near the filter inlet, wouldn't this be an issue with the carpeting/ foreground plants not receiving the adequate CO2 ?


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## Zeus. (23 Mar 2021)

Every tank is different but the aim the same, to have a even [CO2] (carbon dioxide concentration) though out the whole tank so that CO2 gets delivered to every plant you whish to grow, plus maintain that [CO2] from lights on for the main part of the photo period.

The Aim with the CO2 bubbles/mist is to delay them reaching the tank surface, having them rise in the main output jetted to front of tank pushed right down to the substrate then along the substrate. You will know when you have achieved this as your tank will look like '7up' - mine did  ( well thought it looked like Gin and Tonic.)

Having the CO2 being sucked into the filter can work well as is basically using the filter as a CO2 reactor, if any CO2 bubbles/mist don't get sucked in and go straight to the surface of the tank they have limited time to dissolve. Also filters can only handle so much CO2 then then begin the 'burp' due to the build up of CO2 gas, I used this on a FX6 and I was limited to how much CO2 I could inject before the burping started, also CO2 can dissolve your seals in the filter also - but never heard of anyone having an issue. Many folk use low level CO2 injection and use the filters as reactors.

For higher level [CO2] and bubble free (except pearling) CO2 reactors are popular with many folk making DIY ones as the commercial products are not that impressive IMO/IME

I prefer the intake of the filter as low as possible so it removes the water near substrate which many not have a as high [CO2]. Having said that I do have on one of may tanks with the intake very high, however I have twin Maxspact Gyres forcing the CO2 enriched water right round the tank and my tank to output ratio is well above the x10 advised guideline at certain times of day, the guidelines are there to help and not rules. Your plants will tell you when you have it right.

So play the the diffuser placement and see what works well and suits you for viewing as well


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## Driftless (23 Mar 2021)

I am not a fan of spray bars, particularly in that size tank.  See this article and look at the last graphic on the page.  Surface agitation & gaseous exchange in CO2 injected tanks


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## aquascape1987 (23 Mar 2021)

I have a similar set up with the spray bar on a 60cm wide tank, however my volume is approx double this. I inject co2 into a jbl diffuser on the flow line going back to the filter, and have no problems with burping when injecting co2 to get up to a stable 1.3ph drop and lime green on the drop checker.  I find the Jbl ones produce finer bubbles than the Co2 Art ones, although you need to be careful to tighten them tight so that bubbles don’t escape around the membrane. Also no issues with damage to the filters.. Although I do use 2 x filters and inject into both, so this obviously reduces the amount that each filter has to handle. This gives results in the tank almost as good as a reactor, with no 7up effect. I also prefer a longer build up period for CO2 before lights on to get my drop, so instead of 1 to 2 hours before, mine comes on 4 hours before, which means the bubble count is less. It took me a while though to tune in stable CO2 this way, but for me was worth it, as I have stable  high levels of CO2, no 7up effect, and also no burping of filters. My fish also seem to prefer a longer but slower injection rate as well.

Incidentally, my twinstar outlet is at the back on one side only, below the spraybar, and when it goes off, it sends bubbles to the front, down the glass and then they get all round the tank, even though the input is on one side only 🤷🏻‍♂️.

If it were me, I’d invest in an in line diffuser, but if you are sticking with the in tank diffuser, I’d first experiment with it next to the filter intake pipe, and see if you can get your desired level using the filter as a reactor, without it burping 😁


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## Zeus. (23 Mar 2021)

aquascape1987 said:


> Incidentally, my twinstar outlet is at the back on one side only, below the spraybar, and when it goes off, it sends bubbles to the front, down the glass and then they get all round the tank


Twinstar is a great way to check the flow in tank IMO/IME



aquascape1987 said:


> I’d invest in an in line diffuser



+1, even on the outlet they work well.


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## JoshP12 (23 Mar 2021)

I'd put the CO2 diffuser into the inlet of your filter intake. And ensure your spraybar sprays right down the front and swoops to the back. 

Put the inlet as close to substrate and diffuser as possible.


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## ceg4048 (23 Mar 2021)

MMonis said:


> After some research I thought of getting a Fluval Spray bar kit as it will fit well into my Fluval 106 cannister filter output. So no additional pipework/tubing changes or mods (to accomodate lily pipes).
> I have also had poor circulation in the tank with the existing Fluval standard outlet, so hoping that the spray bar will solve the issue and provide both good circulation and surface agitation.
> 
> Since the length of my aquarium is 60 cms, I will need to connect both bars (15 cms each) so that the entire tank length is covered for circulation.


Hello,
             It is not always necessary to run the spraybar along the entire length of the tank. Be mindful when connecting additional bars that the pressure drop across the extra length will reduce the kinetic energy of the flow streams and may reduce the effectiveness of the spraybar assembly.  A better strategy is to first use a single bar mounted at the center of the tank length and evaluate the effectiveness prior to adding a second bar. If you decide to use two bars then I suggest that you also do not fill the cannister  to the brim with media. Remove all the stone type media and only use several coarse foam pads to improve flow rate.

Also review the sticky Water flow in the planted aquarium? at the top of this forum section.

Cheers,


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## Mark Nicholls (23 Mar 2021)

Here's a vid of my pkacement


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## MMonis (24 Mar 2021)

Driftless said:


> I am not a fan of spray bars, particularly in that size tank.  See this article and look at the last graphic on the page.  Surface agitation & gaseous exchange in CO2 injected tanks


If I think of good gaseous exchange and surface agitation, I know that my existing Fluval 106 outlet doesn't provide that. Hence, the move to either lily pipes or a spray bar.
If I look at steel lily pipes then there is only the jet outflow type (don't want to get into glass lily pipes as I will end up breaking them more and its also difficult to maintain them) and I feel the flow maybe too concentrated for my setup since I plan to grow a carpet.


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## MMonis (24 Mar 2021)

aquascape1987 said:


> If it were me, I’d invest in an in line diffuser


After some further reading, I think this is what I am going to invest in. Feels like it has more pros than the in-tank diffusing method.


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## MMonis (24 Mar 2021)

ceg4048 said:


> Hello,
> It is not always necessary to run the spraybar along the entire length of the tank. Be mindful when connecting additional bars that the pressure drop across the extra length will reduce the kinetic energy of the flow streams and may reduce the effectiveness of the spraybar assembly.  A better strategy is to first use a single bar mounted at the center of the tank length and evaluate the effectiveness prior to adding a second bar. If you decide to use two bars then I suggest that you also do not fill the cannister  to the brim with media. Remove all the stone type media and only use several coarse foam pads to improve flow rate.
> 
> Also review the sticky Water flow in the planted aquarium? at the top of this forum section.
> ...


Really great advice, and this has made me decide to do a DIY spray bar with different lengths and check what works out best.


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## MMonis (11 May 2021)

I have setup a DIY spraybar using PVC and drilled 6 holes with a 1/8 drill bit, spaced 3 inches apart. 
Have set the CO2 diffuser close to the intake of the filter.
Here is a video showing the flow. 
Does this seem right and any feedback on it to be improved ?


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## Hufsa (11 May 2021)

Looks vigorous. What is the clear hose kinked into the tank? Outlet? The kink of the hose will be cutting off a lot, you should get a U piece to go over the glass edge


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## MMonis (11 May 2021)

Hufsa said:


> Looks vigorous. What is the clear hose kinked into the tank? Outlet? The kink of the hose will be cutting off a lot, you should get a U piece to go over the glass edge


The kink is on the intake to the filter. Yep, have to fix that during this week


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## MMonis (31 May 2021)

I haven't noticed burping in the canister filter when placing the diffuser under the filter intake as shown in the above video. 
However, I am unable to figure out if the CO2 is being dispersed correctly by the spray bar or most of it is just escaping. How does one figure this out ?


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## Paul Willi (31 May 2021)

Try moving your drop checker to all areas of your tank over time and if it's always lime green during lights on then you getting good distribution. Can help to have more than one drop checker when setting up.


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## ceg4048 (1 Jun 2021)

MMonis said:


> I haven't noticed burping in the canister filter when placing the diffuser under the filter intake as shown in the above video.
> However, I am unable to figure out if the CO2 is being dispersed correctly by the spray bar or most of it is just escaping. How does one figure this out ?


Hi,
    Whenever you make a change to your CO2 technique you should perform what we like to call a CO2 profile. This entails taking a series of pH measurements at the time that the gas goes ON and subsequently every hour or half hour until lights OFF, or at least gas OFF. Record the data and keep records so that you can compare the effectiveness of the change you made. Ideally, you'd like to see a 1 pH unit decrease from gas ON to Lights ON, and then you'd like to see that minimum value maintained all the way to gas OFF. It's difficult to get it perfect, but getting to within 10% is fine. Adjust the injection rate to achieve this. If you are pumping gas into the filter intake and if only a minimal amount of bubbles exit the spraybars then that is usually a good indication that your method is effective. If a lot of bubbles are spurting out through the spraybars then this is less effective and can be annoying but your pH profile will tell you how effective you are. There is no need to move DC around or to have multiple DCs.

Of course, that is only half the story. You also need to have good filter flow rate and the output needs to be distributed evenly across the length of the tank, so the spraybar holes should be pointed straight ahead.

Ultimately, it is the plants that will tell you whether your technique is successful or not. If you see new growth and if the plants do not show evidence of CO2 shortfall then you can be certain that you were successful.

Cheers,


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## MMonis (7 Jun 2021)

Thanks @ceg4048 for the detailed reply. Your inputs are always so helpful.



ceg4048 said:


> Whenever you make a change to your CO2 technique you should perform what we like to call a CO2 profile. This entails taking a series of pH measurements at the time that the gas goes ON and subsequently every hour or half hour until lights OFF, or at least gas OFF. Record the data and keep records so that you can compare the effectiveness of the change you made. Ideally, you'd like to see a 1 pH unit decrease from gas ON to Lights ON, and then you'd like to see that minimum value maintained all the way to gas OFF. It's difficult to get it perfect, but getting to within 10% is fine. Adjust the injection rate to achieve this. If you are pumping gas into the filter intake and if only a minimal amount of bubbles exit the spraybars then that is usually a good indication that your method is effective. If a lot of bubbles are spurting out through the spraybars then this is less effective and can be annoying but your pH profile will tell you how effective you are. There is no need to move DC around or to have multiple DCs.


Attempt 1:
I increased the bubble rate from 1 to 2 bps and following was the pH profile measured by API Drop Test Kit:
9:45 am : Before CO2 on: 7.0
11 am: 1 hr after CO2 on : 6.6
12 noon: 2 hrs after CO2 on: 6.4
1 pm: 3 hrs after CO2 on, lights on (sunrise: 30 min ramp up) : 6.4
1:30 pm : All lights on at 35% intensity : 6.4
The CO2 remained between 6.4 and 6.2 thereafter, but since I could not achive the 1pH drop by lights on, I abandoned this approach

Attempt 2 (next day):
I increased the bubble rate from 2 to 2.5 bps and following was the pH profile measured by API Drop Test Kit:
9:45 am : Before CO2 on: 7.0
11 am: 1 hr after CO2 on : 6.4
12 noon: 2 hrs after CO2 on: 6.2
1 pm: 3 hrs after CO2 on, lights on (sunrise: 30 min ramp up) : 6.1/6.0
1:30 pm : All lights on at 35% intensity : 6.1/6.0
This remained stable till the CO2 off at 4:30pm (lights start dimming from 5:30pm and - sunset and switch off at 6pm)
However, the drop checker seems yellow, so am not sure if I am actually overdosing CO2. At the moment I only have Amano shrimps in the tank but was wondering if this would be an issue when I add fish to the tank. I do not have an air stone or skimmer, but relying completely on the surface agitation by the spray bar.




I am kind off doubting the tests done using the API Drop Test Kit as the lowest it measures is 6.0 and am not sure if my pH drops below that or not. Also, the chart color between yellow (6.0) and faint-green (6.4) is difficult to judge.



ceg4048 said:


> Of course, that is only half the story. You also need to have good filter flow rate and the output needs to be distributed evenly across the length of the tank, so the spraybar holes should be pointed straight ahead.


I think I have a decent flow as I can see that the leaves are gently swaying. The spray bar runs accross the tank and has 6 holes roughly 1/8" diameter. Is there a way to test if the flow is a complete circular motion by adding something to the tank?


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## ceg4048 (8 Jun 2021)

MMonis said:


> I think I have a decent flow as I can see that the leaves are gently swaying. The spray bar runs accross the tank and has 6 holes roughly 1/8" diameter. Is there a way to test if the flow is a complete circular motion by adding something to the tank?


Hi Monis,
              Yes, you can cut a tiny piece of paper, perhaps pin-head size, and drop it on the surface, then watch it's path through the water. This will show you the general flow field that the spraybars create. Do this at as many locations as you want along the length of the tank (middle, corners and so forth). What you hope to see is that the paper heads toward the front glass hand heads rapidly downward along that front pane, then it should head towards the rear and then up along the rear pane. Of course, the speed will peter out and it may start to drift away from this ideal path, but you'd like to see it last at least half way towards the rear.

In this way you will be able to visualize the flow. This technique is not dissimilar to what is done in a wind tunnels using smoke to visualize air flow around an object such as an automobile or airplane.


MMonis said:


> following was the pH profile measured by API Drop Test Kit:


I highly recommend to anyone injecting CO2 to invest in a quality pH probe and pH probe calibration solution. It never ceases to amaze me how many posts I see where the hobbyists is giddy at the thought of spending megabucks on some fancy high powered light (which ironically is the root of all evil) and yet never give a thought to spending money on a good pH probe. Your money should always be spent first and foremost on CO2 problem solving because about 95% of all problems in a CO2 injected tank is due to poor CO2. Let that sink in for a moment... CO2 is always problematic and even if it's perfect today it's a sure thing that it will be somewhere between imperfect and catastrophic a month from now. I suggest investing in any of Hanna's multi-probe such as their pH/TDS/Temp probe.
It's difficult to comment on the yellow DC as there are so many factors such as what kind of water is placed in the DC, accuracy of the reagent and so forth.

Cheers,


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## erwin123 (8 Jun 2021)

Help with Algae and Lack of Plant Growth
					

Again, thank you for your response a Ceg!  I guess I will have to remove the floating plants then, which is a shame because I do like them, but not enough to sacrifice the rest of the plants.   I think the holes in the spray bar are pointing in the same direction, but I will check. A couple of...



					www.ukaps.org
				




From another thread, I thought the 1 pH drop is the drop from the gassed out pH, not from the pH just before CO2 switches on?


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## SudhirR (8 Jun 2021)

erwin123 said:


> Help with Algae and Lack of Plant Growth
> 
> 
> Again, thank you for your response a Ceg!  I guess I will have to remove the floating plants then, which is a shame because I do like them, but not enough to sacrifice the rest of the plants.   I think the holes in the spray bar are pointing in the same direction, but I will check. A couple of...
> ...



Both fully degassed pH and the pH at co2 injection on should remain the same. Are you noticing a marked difference? 


Sent from my iPhone using Tapatalk


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## erwin123 (8 Jun 2021)

SudhirR said:


> Both fully degassed pH and the pH at co2 injection on should remain the same. Are you noticing a marked difference?
> 
> 
> Sent from my iPhone using Tapatalk



Hi Yes there is a difference for my tank water.

Like Katie in the other thread who has a 0.4 difference,  I have a 0.5 difference between degassed pH and pH just before CO2 turns on.  I don't need to wait 24 hours for it to show a difference- waiting 12 hours I already have a 0.5pH difference.

So I'm following the discussion on what would be the correct target pH to learn more.

I'm using an Apera Ph20 meter which is calibrated to a 4.0/7.0 solution.


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## aquascape1987 (8 Jun 2021)

SudhirR said:


> Both fully degassed pH and the pH at co2 injection on should remain the same. Are you noticing a marked difference?



I don’t think that this is very common is it? I have never experienced this in any of my own tanks ever, since starting to inject CO2. There is always some residual CO2 left in the water from injection the previous day, by the time the CO2 comes back on again in my experience, so there would always be some Co2 to off gas to get your starting pH.


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## ceg4048 (9 Jun 2021)

erwin123 said:


> Like Katie in the other thread who has a 0.4 difference, I have a 0.5 difference between degassed pH and pH just before CO2 turns on. I don't need to wait 24 hours for it to show a difference- waiting 12 hours I already have a 0.5pH difference.
> 
> So I'm following the discussion on what would be the correct target pH to learn more.





SudhirR said:


> Both fully degassed pH and the pH at co2 injection on should remain the same. Are you noticing a marked difference?





aquascape1987 said:


> I don’t think that this is very common is it? I have never experienced this in any of my own tanks ever, since starting to inject CO2. There is always some residual CO2 left in the water from injection the previous day, by the time the CO2 comes back on again in my experience, so there would always be some Co2 to off gas to get your starting pH.



That is correct. There is always some residual CO2 left in the water, however, the amount of residual is dependent on water temperature, whether the tank is top is closed or open as well as the degree of surface agitation. Also consider the accuracy and calibration quality of the device being used to measure the pH. This is normal and is not cause for concern. You can either use the reading you get from the residual CO2 or you can use the natural pH of the water as a reference. Whichever works for you will suffice. The 1 Ph drop is just a rule of thumb not some kind of cliff that your tank will fall off of if violated.  
Some folks are rightfully concerned that using the residual reading may harm the fish so it is safer to use the natural pH as a reference for the drop. This is sound reasoning, especially for the inexperienced. Others use the residual reading and are fine. Fish can adapt to surprising levels of hypercapnia, within limits, and as long as it is done gradually.
More important than the number used as a reference is that your distribution is excellent. When this is achieved you'll find that you can lower the injection rate and still obtain a good pH drop and good, even CO2 levels throughout the tank.

This highlights yet another complicated nuance of CO2 technique. Obviously, if the injection rate is excessive during the day this is a problem, and blood CO2 levels acidify the blood and thus reduces the capacity of hemoglobin (in fish) and Hemocyanin (in inverts) to hold on to oxygen molecules. Fish and inverts however have a defense mechanism against blood acidifcation and that is their bodies release bicarbonate into the bloodstream to buffer the blood against internal pH depression. Additionally, during the photoperiod the plants release oxygen into the water column. The most dangerous time  is early in the morning before lights ON, when the oxygen level is depleted and the plants and bacteria compete with the fish for oxygen. So the combination of elevated CO2 and low oxygen is less than ideal. That is why some folks employ air-stones at night to reduce CO2 levels and to help with oxygen. This is a Catch-22 however because the gas injection rate must now be high enough to compensate for the purged residual CO2.

Cheers,


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## SudhirR (9 Jun 2021)

aquascape1987 said:


> I don’t think that this is very common is it? I have never experienced this in any of my own tanks ever, since starting to inject CO2. There is always some residual CO2 left in the water from injection the previous day, by the time the CO2 comes back on again in my experience, so there would always be some Co2 to off gas to get your starting pH.



My co2 goes off at 5 pm and my aeration comes on. And the pH goes up till about midnight or so and remains almost constant till 11 am when the aeration stops and the co2 turns on. 

My co2 chart is here: CO2 Already Dialled In, But Rechecking

Also I have good amount of surface agitation and flow in my tank. Now I am confused as to at what point the degassed pH needs to be measured. I was thinking it’s at the point when all the co2 is degassed and the PH is fairly constant. Pls let me know the correct interpretation. 


Sent from my iPhone using Tapatalk


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## aquascape1987 (9 Jun 2021)

SudhirR said:


> I was thinking it’s at the point when all the co2 is degassed and the PH is fairly constant. Pls let me know the correct interpretation.


I think that is the correct starting point. Just that most folks need to let their water de gas/actively de gas their water to be able to get this pH measurement.


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## MMonis (9 Jun 2021)

ceg4048 said:


> I suggest investing in any of Hanna's multi-probe such as their pH/TDS/Temp probe.


Would this pH meter from Hanna suffice : Hanna HI-98100 Checker plus pH tester
Seens these products are pretty expensive


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## erwin123 (10 Jun 2021)

Amazon product
I'm using a budget Apera pH meter. Hey, it got 3370 reviews in Amazon. When I first got it and put it into the calibration solution, it was only 0.1 off from the reference solutions.

Amazon product
Here's the more expensive multi-test.


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## arcturus (10 Jun 2021)

MMonis said:


> Would this pH meter from Hanna suffice : Hanna HI-98100 Checker plus pH tester
> Seens these products are pretty expensive



Most of them usually suffice for a (short) while. Low quality devices tend to have low quality probes that require frequent calibration. The probe will eventually start giving erroneous readings. Better to invest on a device with a replaceable probe (such as the GHM Greisinger 609850 or a better device). When the probe fails, then invest on a good quality probe since it will last longer and you will end up saving money in the long run. But it makes absolutely no sense to put a lot of money on a high-tech setup with CO2 injection and then trying to save money buying a low-tech device that does not enable you to properly measure CO2...


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## ceg4048 (11 Jun 2021)

MMonis said:


> Would this pH meter from Hanna suffice : Hanna HI-98100 Checker plus pH tester
> Seens these products are pretty expensive


Hi Monis,
              Wow, I'm really shocked at the pricing although I'm not familiar with the Danish Krone. According to the currency conversion charts that is about $65 in US currency, whereas in USA that same probe retails for about $40. So that is not too bad for a probe with two point calibration and with a replaceable probe. These are the two most important features and is definitely better than reagent based test kits. My choice would be for the HI-98108, shown just to the right on that page, but that cost 574 Krone. Again, compare how much money people are willing to spend for fancy lights.


SudhirR said:


> Also I have good amount of surface agitation and flow in my tank. Now I am confused as to at what point the degassed pH needs to be measured. I was thinking it’s at the point when all the co2 is degassed and the PH is fairly constant. Pls let me know the correct interpretation


Hi, you are over-thinking this problem. As mentioned, the natural pH of your water should be the starting point. All you have to do is take a sample in a bottle and shake it up for 5 minutes or so, or let it sit on the counter for an hour. Whatever pH is measured is a good starting point. Subtract 1 and there is your target. Keep it simple. You can always make adjustments from there and as your plants grow in you very well may need to adjust the target downward - but look at your plants. Are they healthy and algae free? Are the fish healthy? Ultimately, those are the only parameters you need to worry about. 

Do not fret over what number to use. In fact, people using ridiculous amounts of lighting often require a much larger pH drop to avoid algal blooms.

Here is an example of my tank using absurdly high lighting. In my case hair algae was a constant companion, even with good flow/distribution, so it was necessary to use a higher injection rate if I didn't want to reduce the lighting. Over a period of a few weeks I was able to drop the pH by a full 2 units from the natural pH of the tank . This was accomplished slowly and carefully while observing the fish. Again, when done deliberately and carefully the fish are resilient and easily adapt. The CO2 was on for only 4-5 hours and that allowed the fish to recover.





So there is a wide margin if your distribution is adequate. Folks often have difficulty with their fish adapting to CO2 because of poor flow /distribution, so concentrate on that, observe the tank and do not worry about which number to use,

Cheers,


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## MMonis (20 Jun 2021)

Hi @ceg4048 
I purchased the Hanna phep HI-98107 pH meter, as this was the only one available for delivery in Denmark at the earliest. Following is the pH profile I ran today:

TimepHRemarks10:006.9CO2 turned on (same pH value before CO2 on as well)11:006.31 hr after CO2 on12:006.22 hrs after CO2 on12:306.22.5 hrs after CO2 on13:006.23 hrs after CO2 on13:306.23.5 hrs after CO2 on14:006.24 hrs after CO2 on; Lights on (sunrise start - sunrise period 30 mins)14:306.24.5 hrs after CO2 on; 30 mins after Lights on (RGB - 40% intensity)15:006.25 hrs after CO2 on, 1 hr after Lights on15:306.2/6.35.5 hrs after CO2 on; 1.5 hrs after Lights on16:006.2/6.36 hrs after CO2 on, 2 hrs after Lights on17:006.37 hrs after CO2 on; 3 hrs after Lights on18:006.38 hrs after CO2 on; 4 hrs after Lights on18:306.3CO2 off; 4.5 hrs after Lights on19:006.430 mins after CO2 off; 5 hrs after Lights on19:306.61 hr after CO2 off; 5.5 hrs after Lights on (sunset start - sunset period 30 mins)20:006.71.5 hrs after CO2 off; Lights off21:006.82.5 hrs after CO2 off; 1 hr after Lights off

I was expecting that around 13:00 pm I would get the pH drop by 1, but it never went down below 6.2 throughout. Since I have started this aquarium around 50 days ago and using Tropica Aquarium Soil, could the soil be preventing the pH from dropping lower than 6.2 ?
Any insights based on the pH profiling above ?

Regards,
Mel


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## ceg4048 (21 Jun 2021)

MMonis said:


> I was expecting that around 13:00 pm I would get the pH drop by 1, but it never went down below 6.2 throughout. Since I have started this aquarium around 50 days ago and using Tropica Aquarium Soil, could the soil be preventing the pH from dropping lower than 6.2 ?
> Any insights based on the pH profiling above ?


Hi Mel,
          OK, well, first of all, it's really important to understand the reason we are using a pH drop. I feel that a lot of folks don't understand why we do it. We just tell them they should do it, and they follow suit, not always understanding the mathematics of the method. As you probably know (or perhaps were told) if you measure the pH of the tank water and plug that reading into the infamous pH/KH/CO2 chart you will almost always get the wrong CO2 value because the tank water is affected not only by the Carbonic acid produced by the CO2, but the pH is driven even lower due to the organic acids present in the water. So folks who are unaware of this phenomenon will always read a higher CO2 value than there actually is in the water.

So we take a pH reading at the start and that gives us a pH value composed of a [pre-CO2 induced acidity + Organic acidity] then we take a reading later in the day to get a [Co2 induced acidity + Organic acidity].

When we say find the "pH drop" what we are really saying mathematically is to subtract the CO2 induced reading from the pre-CO2 induced. A geek would be write this as a simple equation:

[pre-CO2 induced acidity + Organic acidity] - [Co2 induced acidity + Organic acidity]

Which then becomes:
pre-CO2 induced acidity + Organic acidity - Co2 induced acidity - Organic acidity

The expression "Organic acidity" cancels because there is one with a plus (+) and one with a minus (-).
So the equation now reduces to:
pre-CO2 induced acidity  - Co2 induced acidity
This is exactly what we are trying to do. Since BOTH pre and post CO2 reading are equally affected by the same organic acid, taking the DIFFERENCE between the two readings effectively eliminates the organic acid contribution from the equation. We can be confident that over the span of a few hours the organic acid content of the tank water will not appreciably change. We assume it will have the same value and therefore subtracting one pH reading from the other, even though we do not know exactly the quantity of the organic contribution, will cancel the organic acid content.

Now, in the ideal world we'd be able to go to the chart with your numbers:
pre-CO2 is 6.9 and post CO2 is 6.2
For any KH we would plug 6.9 in the chart and the chart would returns a fictitious CO2 value.
Then we would plug 6.2 in the chart and it would returns another fictitious CO2 value. Ideally, we would subtract one from the other and this would tell us our true CO2 value - except, now we get to the second problem with the pH/KH/CO2 chart. Not only does it assume that the acidity of the water is caused ONLY by CO2, but it also assumes the KH of the water is ONLY cause by carbonate. As we should know, our KH test kit is NOT a KH test kit. It is an ALKALINITY test kit and the reading it returns is actually due to many possible components not named carbonate or bicarbonate.

The third problem with the chart is that the data is not linear, it's logarithmic because pH itself is logarithmic. We've kind of figured out that a drop of about 1 unit will give you about 30-40ppm but these are just basic numbers. Everyone's alkalinity composition differs as does their tank acid contribution. This is why I'm always warning people to NOT get caught up in chasing numbers as if they were the Holy Grail. At best they are rules of thumb. You still have to monitor your fish and plants.

This was a really long winded way of saying "No it has nothing to do with you're soil and everything to do with your injection rate and flow/distribution." In any case, just live with your 6.2 for the moment and when you have a lot of time to experiment with the injection rate and are able to monitor your fish make the adjustments as needed. If your plants are happy with this configuration then leave it be. If you are experiencing CO2 related algae or CO2 related faults then you might want to think about trying to optimize further. Having said that, it should not take 4 hours to drop the pH 0.7 units and as I mentioned, that is most likely due to some combination of injection rate, diffusion method, excessive surface agitation and flow/distribution.

Continue to monitor with your new probe. Keep the tip moistened and calibrate frequently. Every time you make a change to your setup repeat the exercise and record the data so that you can analyze at a later date. Avoid the pH/KH/CO2 charts as if it were the plague.

Cheers,


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## Cdytebg (18 Aug 2022)

Love Reading this content. Only yesterday I looked at the CO2 chart and it appeared I have levels of 50+ppm on CO2

Now I can see why it is inaccurate


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