Dialling in the CO2 injection Rate and CO2 Profiles

[Cavalier_Steve]

Yep, exactly that. The controller is always sensing and trying to control the Co2, but the timer will only allow it during your injection period.

Thank you both kindly for answering my questions so quickly, I’m really keen on trying this setup myself.
Yes I wasn’t sure if the pH controller would loose its calibration over multiple power cycles over a month or something weird like that.
Thanks again for your help!
Edit: Sorry for high jacking this thread 🤦‍♂️🙂
Kind regards,
Steve.

 

[Sacul]

Thank you for this write up. After searching for weeks for info, this is the best write up I've seen and very helpful. I just need a bit of clarification. After alot of adjusting CO2 and testing pH I think I'm kind of stable.
Tank water sat 24h in a glass pH 8.23
Tank Kh 8
I can get a drop to 7.2 and keep it stable within 0.1 for the rest of the lights on duration. According to the pH drop of 1 that should be around 30ppm ish. According to the charts it's alot less. Should I just ignore the chart and stick with what I've got? I can't seem to drop any lower, if I turn the CO2 up any more it just keeps dropping the pH until CO2 off and I can't stabilize it.
Thanks @Zeus. for all your help

 

[Zeus.]

According to the charts it's alot less. Should I just ignore the chart

Yes, the chart is a complete waste of time.

 

[Sacul]

Time it takes to get your target CO2 level
The time it takes to reach a CO2 concentration of 30ppm varies with tank size and injection method. About 2hrs is normal for a 50 litre tank, but bigger tanks can take 4 to 5 hours plus.

Hi
I'm reading through your post again to make sure I've not missed anything. When your talking about the time it takes to reach 30ppm, are you talking about 2hrs of CO2 being injected before the lights come on? Assuming that's what you mean, having a bigger tank I could push the time back at which the CO2 turns on to try and get better saturation by the time lights are on.

 

[KirstyF]

Hi
I'm reading through your post again to make sure I've not missed anything. When your talking about the time it takes to reach 30ppm, are you talking about 2hrs of CO2 being injected before the lights come on? Assuming that's what you mean, having a bigger tank I could push the time back at which the CO2 turns on to try and get better saturation by the time lights are on.

Hi There. Yep that’s what is being said.

However long it takes to get to your 1ph drop is just however long it takes and you ideally want to already be there when the lights come on.

I’ve a very big tank and it takes 3.5hrs before lights on, with 2 reactors, to hit that 1ph drop.

If you’re getting a pretty stable level through your photo period but not quite getting to a 1ph drop by the time the lights come on then you can likely leave everything as it is but just turn the Co2 on a bit earlier.

There is a solid argument to say that it takes a wee while for the plants to get going so if it’s not spot on 1ph the very moment you have lights, it’s not the end of the world, but it’s a good target to have and will make sure that the Co2 is fully available as soon as the plants need it. 😊

 

[Sacul]

If you’re getting a pretty stable level through your photo period but not quite getting to a 1ph drop by the time the lights come on then you can likely leave everything as it is but just turn the Co2 on a bit earlier.

I thought I was getting pretty stable level but I've noticed it is still dropping towards the evening. My thinking was if I turn it on even earlier, was 3hrs now testing 4hrs to see if I can get it to drop even lower before lights on then hopefully it will stable out a bit more during the photo period

 

[Hufsa]

I thought I was getting pretty stable level but I've noticed it is still dropping towards the evening. My thinking was if I turn it on even earlier, was 3hrs now testing 4hrs to see if I can get it to drop even lower before lights on then hopefully it will stable out a bit more during the photo period

My understanding is that injection rate controls how fast your drop is, but surface agitation / off-gassing controls how steady the level is and effectively stops the CO2 concentration from getting higher than you want.
The final range you end up in is a result of both factors.

Therefore if you want a steadier level during lights on, I would look at your surface agitation. Then after that adjust injection as needed.

 

[KirstyF]

I thought I was getting pretty stable level but I've noticed it is still dropping towards the evening. My thinking was if I turn it on even earlier, was 3hrs now testing 4hrs to see if I can get it to drop even lower before lights on then hopefully it will stable out a bit more during the photo period

What is your surface agitation like? Whilst it may seem counterintuitive, a good level of surface movement IMO helps to stabilise things too. 😂 Lol. Last message just popped up so……what @Hufsa just said. 👍

I would therefore make sure you are getting a good surface ripple, do a profile again and then start a bit earlier if you need to.

 

[Sacul]

Therefore if you want a steadier level during lights on, I would look at your surface agitation

This is what I though aswel from what I have read, I have a 3200lh powerhead pointed at the surface of the tank aswel as a 1450lh filter pointed at the surface plus a skimmer so would say I have pretty good surface agitation. It is a 5ft tank so more agitation on one side than the other but still movement across the whole surface.

 

[Zeus.]

Hi
I'm reading through your post again to make sure I've not missed anything. When your talking about the time it takes to reach 30ppm, are you talking about 2hrs of CO2 being injected before the lights come on? Assuming that's what you mean, having a bigger tank I could push the time back at which the CO2 turns on to try and get better saturation by the time lights are on.

Yes

a bigger tank I could push the time back at which the CO2 turns on to try and get better saturation by the time lights are on.

A bigger tank may take longer and a small tank less time.

I thought I was getting pretty stable level but I've noticed it is still dropping towards the evening. My thinking was if I turn it on even earlier,

My understanding is that injection rate controls how fast your drop is, but surface agitation / off-gassing controls how steady the level is and effectively stops the CO2 concentration from getting higher than you want.
The final range you end up in is a result of both factors.

Therefore if you want a steadier level during lights on, I would look at your surface agitation. Then after that adjust injection as needed.

@Hufsa nails it, it is a blend of the injection rate and the surface agitation. With higher surface agitation you will need a higher injection rate to compensate for the increase loss of CO2 from the surface, But the pH drop will be quicker and more stable.

 

[Sacul]

With higher surface agitation you will need a higher injection rate to compensate for the increase loss of CO2 from the surface, But the pH drop will be quicker and more stable.

So possibly my injection rate is too high if the pH keeps dropping. My thinking was, I think I have enough surface agitation but because the pH keeps dropping, if I push the CO2 on time back an hour it could drop that little bit more before the photo period. As long as the livestock is still safe then hopefully stable out a bit more during the photo period.

 

[KirstyF]

Can you post your full profile results from gas on to lights off? Might help folks to give some advice specific to your situation. 😊

 

[Sacul]

Can you post your full profile results from gas on to lights off? Might help folks to give some advice specific to your situation. 😊

After doing a new pH profile yesterday my drop seems to have gone back to stable. Not sure what happened on that odd day where it was out with the last reading being 7.16. I did the degas jar shake which made my degassed pH value higher than my 24hr sat glass of water.
24hr glass 8.23
Jar shake 8.32
At lights on I was at 7.34 and lights off 7.29.
Although it seems like I'm getting the 1ph drop, my drop checker still isn't lime green. It's still more of a darker green. Is this a problem or not really?

 

[_Maq_]

Excuse me but this is something I don't quite accept. True, I've never injected CO2.
My reasoning goes like this: What are the driving forces of photosynthesis? Light and CO2. Are they in stable supply in the (underwater) nature? No, never. There may be approximate stability from day to day, but never during the day. "Stability during photoperiod" is something the plants never enjoy in the nature.
It is true that plants respond to environmental factors, and they do adjust their photosynthetic apparatus to light and CO2 conditions. Par example, if CO2 concentration is elevated, they suppress chlorophyll creation (while anthocyanin creation remains the same, and thus plants are getting red). Similarly, they react to an amount of light reaching individual leaves. However, these adaptations do not happen within hours. These reflect average conditions in the range of several days to weeks.
So, I don't see any necessity to seek "stability during photoperiod". I admit that plants may benefit energetically from "longterm stability" but I don't believe they re-build their proteins due to hour-to-hour changes in illumination or CO2 concentration. Such rapid reactions would certainly turn out to be a competitive disadvantage.
I repeat, I've never injected CO2. If your observations suggest something different from what I've noted above, please, describe your experience in more detail.

 

[Wookii]

Excuse me but this is something I don't quite accept. True, I've never injected CO2.
My reasoning goes like this: What are the driving forces of photosynthesis? Light and CO2. Are they in stable supply in the (underwater) nature? No, never. There may be approximate stability from day to day, but never during the day. "Stability during photoperiod" is something the plants never enjoy in the nature.
It is true that plants respond to environmental factors, and they do adjust their photosynthetic apparatus to light and CO2 conditions. Par example, if CO2 concentration is elevated, they suppress chlorophyll creation (while anthocyanin creation remains the same, and thus plants are getting red). Similarly, they react to an amount of light reaching individual leaves. However, these adaptations do not happen within hours. These reflect average conditions in the range of several days to weeks.
So, I don't see any necessity to seek "stability during photoperiod". I admit that plants may benefit energetically from "longterm stability" but I don't believe they re-build their proteins due to hour-to-hour changes in illumination or CO2 concentration. Such rapid reactions would certainly turn out to be a competitive disadvantage.
I repeat, I've never injected CO2. If your observations suggest something different from what I've noted above, please, describe your experience in more detail.

Absolutely agree with your references to a natural environment, I have read that many biotopes can completely bottom out the CO2 levels during the photo period.

That said, we are not necessarily trying to replicate a natural environment. Many aquarists (perhaps the majority) are attempting to create a well tended aquatic 'garden', free from 'weeds' - the weeds in our case being algae. Algae free plants are something you very rarely see in nature.

Anecdotally, many users have observed that algae appear to proliferate when there is a lot of variability in CO2 levels in a CO2 injected tank, and that algae appears to be more easily prevented when the CO2 levels are stabilised throughout the photo period. Hence it is a typical recommendation for anyone injecting CO2, particularly in the initial 'set-up' phase, to aim for consistent dissolved CO2 levels.

 

[_Maq_]

algae appear to proliferate when there is a lot of variability in CO2 levels in a CO2 injected tank

Okay, such is perhaps a common wisdom. But do we have any explanation for it?
Unlike higher plants, algae do not modify their photosynthetic apparatus, they only regulate their "breeding". If conditions are favourable, they proliferate. Do they get any advantage from variable CO2 concentrations?

 

[Wookii]

Okay, such is perhaps a common wisdom. But do we have any explanation for it?
Unlike higher plants, algae do not modify their photosynthetic apparatus, they only regulate their "breeding". If conditions are favourable, they proliferate. Do they get any advantage from variable CO2 concentrations?

We don't I'm afraid - the stimuli for algae growth in this hobby seem to remain one of the great mysteries, as I'm sure you know.

In my own broad brush observations, the proliferation of algae always seems to be linked to some sort of instability in the ecosystem of our aquariums. Sudden changes, be those a sudden increase in organics, spikes in ammonia (which you are kind of testing currently), changes in CO2 and oxygen levels - all seem to have the potential for algae to suddenly get a foot hold. In my experience, and with observations of experiences on this forum, the greatest enemy to algae appears to be consistency. All too often the aquarist is keen to turn the tank 'dials', constantly adjusting CO2 delivery, or ferts, or lighting, or water change regime - when the best course of action is just to keep things the same for as long as possible to gain long run stability. In some way maintaining consistent CO2 appears to aid that stability.

It annoys me that I/we don't understand the mechanisms for that - whether there is some competitive mechanism between the plants and algae that is enhanced by stability of the plants environment, or perhaps linked to stability in the microbial community that somehow supresses algal growth, I don't know?

 

[_Maq_]

We have moved a bit, though. Now we don't talk about plants permanently adjusting to changing conditions, but rather about complex influence of variable concentration of CO2 on the system, of which the visible symptom is algae proliferation.
Algae compete not only with higher plants but with non-photosynthesizing microbes as well. CO2 concentration influences pH significantly. Yet CO2 fluctuations in certain range are natural, too.
If CO2 injection is unstable, and consequently carbon availability and pH, it may very well disturb microbial community. Microbes are zonally distributed in line with oxygen concentration, and other factors. pH may influence solubility of various compounds, and redox reactions occur; redox potential is therefore changing. Also, pH directly affects microbes, their preferred value is sometimes quite narrow. I can imagine that irregularity in CO2 concentration may lead to leaching various compounds from sediment to water column.
On the contrary, if the daily rhythm of CO2 concentration is whatsoever but stable, microbes can adjust and do their business in a way that leaves little space for algae.
Yes, I can imagine that, but like you said, @Wookii , it's only guess. And it does not necessarily confirm that it's the plants who suffer from CO2 irregularities most importantly.

 

[Hanuman]

We don't I'm afraid - the stimuli for algae growth in this hobby seem to remain one of the great mysteries, as I'm sure you know.

In my own broad brush observations, the proliferation of algae always seems to be linked to some sort of instability in the ecosystem of our aquariums. Sudden changes, be those a sudden increase in organics, spikes in ammonia (which you are kind of testing currently), changes in CO2 and oxygen levels - all seem to have the potential for algae to suddenly get a foot hold. In my experience, and with observations of experiences on this forum, the greatest enemy to algae appears to be consistency. All too often the aquarist is keen to turn the tank 'dials', constantly adjusting CO2 delivery, or ferts, or lighting, or water change regime - when the best course of action is just to keep things the same for as long as possible to gain long run stability. In some way maintaining consistent CO2 appears to aid that stability.

It annoys me that I/we don't understand the mechanisms for that - whether there is some competitive mechanism between the plants and algae that is enhanced by stability of the plants environment, or perhaps linked to stability in the microbial community that somehow supresses algal growth, I don't know?

Beautifully put.

 

[Zeus.]

Excuse me but this is something I don't quite accept. True, I've never injected CO2.

In nature the order of magnitude of change in [CO2] is small, the our CO2 injected tanks it is large, I think its all to do with the magnitude of change and many find having a stable [CO2] for the photoperiod works. @ceg4048 would give a better answer if active