# Ph profile with pressurized co2



## Puntius (16 Oct 2017)

So im getting a nice 1 unit drop by lights on  later during the lighting phase it drops to around 6.6 - 6.7 I added my profile..below 99% of fish fine only my neon dwarf rainbows at the surface sometimes around 20h30 but not always. All fish active though.. Is this fine it dropping more during the co2 phase.. My kh is 4 just for info. Co2 comes on at 12h00 and lights in by 14h00.

My profile over the weekend 

Friday
Inside tank 18h40 = 6.5 ph
Inside tank 18:40 = 6.8 ph
Inside tank 20h52 = 6.7 ph

Saturday. 
Complete ph profile 

Inside tank 07h25 = 8.2 ph
Inside tank 11h30 = 8.1 ph
Inside tank 12h45 = 7.4 ph
Inside tank 13h15 = 7.3 ph
Inside tank 13h30 = 7.2 ph
Inside tank 14h00 = 7.1 ph
Inside tank 15h10 = 6.8 ph
Inside tank 16h05 = 6.8 ph
Inside tank 17h30 = 6.7 ph

Any comments or tips. 

My water movement is 24 Times my water volume.

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## Edvet (16 Oct 2017)

At low Kh a bigger drop is expected. I would start CO2  a bit earlier to have it a 6.8 at lights on. You can have CO2 off 4 hours after light on.


Puntius said:


> My water movement is 24 Times my water volume.


Sounds good, just volume doesn't neccesarily mean good distribution


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## Puntius (16 Oct 2017)

Edvet said:


> At low Kh a bigger drop is expected. I would start CO2  a bit earlier to have it a 6.8 at lights on. You can have CO2 off 4 hours after light on.
> 
> Sounds good, just volume doesn't neccesarily mean good distribution


Okay cool that does make sense. 100% of plants swaying nicely in the water column... So I'll start my co2, 30 minutes earlier as I noticed ph drops quite quickly. So it won't drop below 6.8 later during the lighting phase as it will be on longer then usually. So do you also shut your co2 of 4 hours after lights on.. 

Any other input on this. 

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## Zeus. (16 Oct 2017)

I get a extra 0.1 to 0.2 pH over the photo period also. Getting a 'table top' profile is tricky.
I've never felt comfortable having the CO2 going off after 4hrs. I'm sure Clive will be correcting me when he sees this post.

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## Puntius (16 Oct 2017)

Zeus. said:


> I get a extra 0.1 to 0.2 pH over the photo period also. Getting a 'table top' profile is tricky.
> I've never felt comfortable having the CO2 going off after 4hrs. I'm sure Clive will be correcting me when he sees this post.
> 
> Sent from Mountolympus via neural interface


Cool so it is normal to get extra ph drops over the photo period. I'll also rather leave my co2 on longer. I might put co2 on 30 minutes earlier to get an extra 0.2 or 0.3 by lights on currently with lower kh. 

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## Zeus. (16 Oct 2017)

I am sure Edvet is right about after 4hrs as it fits with what the 'High Priest' advocates.
But being a newbie and trying to get algea under control I rather have the [CO2] stable for the whole photoperiod ATM. If my tanks was algea free or with more experience I'm sure I would have the confidence to have the CO2 going off sooner.

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## Edvet (16 Oct 2017)

After 4 hours the plants have "eaten"as much as they can and they can do without CO2. You can keep it on longer, but it's a waste of CO2.


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## Zeus. (16 Oct 2017)

So why do the plants still pearl? As if they have had their fill, then photosynthesis would stop and then no O2 as by product. Or is it case of the plants are just slowly consuming CO2 and a little O2 is produced. 
Does the 4hrs still apply with less light in a CO2 tank? Say your tank is established you get a new plant and add it to your tank, you keep the same [CO2] but reduce the intensity so the new plant can adjust its mechanisms to the higher [CO2] after a few weeks you slowly increase the light intensity back to pre new plants levels. 
But during the lower light aclimitasation period for the new plant, the established plants will receive less photons in four hours! So if we do reduce our lights intensity for what ever reason, should we extend our CO2 injection period longer than the first 4hrs of the photoperiod as the plants have yet to get their fill?

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## Edvet (16 Oct 2017)

Shamelessly copying Clive: https://www.ukaps.org/forum/threads/adding-gas-to-low-tech-tank.50986/page-2#post-501162
https://www.ukaps.org/forum/threads/co2-and-water-changes.1132/#post-10761


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## Puntius (16 Oct 2017)

Very good question @Zeus im not bothered waiting co2 but yes if they only need co2 for lets say a total of 6 hours since co2 on why do all the threads say co2 must go of an hour before lights... 

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## Puntius (16 Oct 2017)

Would also definitely want to hear @ceg4048 input on this rather important topic 

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## Edvet (16 Oct 2017)

Puntius said:


> co2 must go of an hour before lights..


So they have the most CO2 available when the light hits. It protects them.
https://www.ukaps.org/forum/threads/cladophora-vile-weed.11320/#post-120485


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## Puntius (16 Oct 2017)

Edvet said:


> So they have the most CO2 available when the light hits. It protects them.
> https://www.ukaps.org/forum/threads/cladophora-vile-weed.11320/#post-120485


No did not say an hour before lights go on. You say co2 must only remain on for 4 hours into the lighting phase. Why do most threads then say co2 must go off an hour before lights go off at night. 

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## Zeus. (16 Oct 2017)

Edvet said:


> Shamelessly copying Clive: https://www.ukaps.org/forum/threads/adding-gas-to-low-tech-tank.50986/page-2#post-501162
> https://www.ukaps.org/forum/threads/co2-and-water-changes.1132/#post-10761


Yes in a plant recieving high light its full after four hours. But if you reduce the intensity it won't be full after 4hrs as it's storage capacity has yet to be reached, as less photons means less complex carbohydrates production. So if your [CO2] falls after 4hrs and the plant hasn't had its fill due to reduced light intensity. The the plant may start adjusting to the lower [CO2] which is bad OFC for the reasons Clive explained!

Not questioning the explanation OFC just after a better personal understanding 

So if are plants in a high light stable [CO2] have had their fill after four hours, if we can would it not be better to reduce the lights intensity. As if the plants are not using the photons of light, there will be more photons avialible for the algea to feed on!

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## Puntius (16 Oct 2017)

Also talking about lights, Clive informed me while back not the have all my lights on initially when lights go on. So my 1 x 10000k  tube goes on 2 hours after co2 on. Then my 2 x 18w leds 6500k goes on at 15h30 and then my last 18w led goes on at 16h00. To give a nice ramp up for the lighting phase. So I would think having co2 on for 4 to 5 hours after all the lights are on should be sufficient then. So that would mean my co2 goes off at around 20h00 or 20h30 then @ceg4048 

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## Zeus. (16 Oct 2017)

My thoughts as well. Having higher light with decreasing [CO2] may be counter productive to plant grow if photosynthesis is limited by the avialible CO2. But if photosynthesis isn't limited by the avialible CO2 it shouldn't be an issue. After all when my lights go off my airstone comes on and it does take some time for the PH to increase. Even 12hrs later the pH is still climbing  very slowly. Just my observations. 

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## Puntius (16 Oct 2017)

Exactly my airstone comes on at 21h30, about 40 minutes before lights off and by around 07h30 my tank co2 is degassed and ph 8.1 again... My co2 does go off at 21h00 used to go off at 21h15 so having it on for that extra 30 minutes is not gonna really waste co2. Still waiting for @ceg4048 for his final confirmation or @Edvet

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## Edvet (16 Oct 2017)

Puntius said:


> Why do most threads then say co2 must go off an hour before lights go off at night.


For the plants you could leave it on. For the fish: at night the plants themselves produce CO2, that added to high values through CO2 dispension might result inl evels to high for fish. Hence using an airstone to diminish the CO2 in the column during lights out.


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## Puntius (16 Oct 2017)

Edvet said:


> For the plants you could leave it on. For the fish: at night the plants themselves produce CO2, that added to high values through CO2 dispension might result inl evels to high for fish. Hence using an airstone to diminish the CO2 in the column during lights out.


I understand that, just asking why you saying co2 can go off after 4 hours since light on... So you still think I can start co2 30 minutes earlier 

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## Puntius (16 Oct 2017)

Puntius said:


> Also talking about lights, Clive informed me while back not the have all my lights on initially when lights go on. So my 1 x 10000k  tube goes on 2 hours after co2 on. Then my 2 x 18w leds 6500k goes on at 15h30 and then my last 18w led goes on at 16h00. To give a nice ramp up for the lighting phase. So I would think having co2 on for 4 to 5 hours after all the lights are on should be sufficient then. So that would mean my co2 goes off at around 20h00 or 20h30 then @ceg4048
> 
> Sent from my SM-G930F using Tapatalk


Too all the experts out there any comments on this  

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## Edvet (16 Oct 2017)

I said 30 minutes earlier because there seemed to be  another pH drop going on after lights on, and i believe it's best to start with optimal CO2 in the column at lights on, so just start a bit earlier.
The 4 hours i stole from Clive. Most hightech tanks light 6-8 hours. You can stop adding CO2 2 hours before lights end.
The whole "protection effect of CO2/Rubisco"against high light levels isn't fully understood as far as i know, though it is shown to be in effect.


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## Puntius (16 Oct 2017)

Edvet said:


> I said 30 minutes earlier because there seemed to be  another pH drop going on after lights on, and i believe it's best to start with optimal CO2 in the column at lights on, so just start a bit earlier.
> The 4 hours i stole from Clive. Most hightech tanks light 6-8 hours. You can stop adding CO2 2 hours before lights end.
> The whole "protection effect of CO2/Rubisco"against high light levels isn't fully understood as far as i know, though it is shown to be in effect.


My lights are on from 14h00 till 22h00 9 hours where all the lights are on from 16h00. So full lighting phase for 5 1/2 hours.. So I will start co2 30 minutes earlier from tomorrow. Then my co2 will go off 2 hours before the lights out at 20h00. And airstone comes on at 21h30 and lights off by 22h15. Sure 1 hour is enough time for plants to warm up. So will be starting my 2 led tubes at 15h00 instead of 15h30 then 3rd tube will go on at 16h00..edited  

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## Zeus. (16 Oct 2017)

Thought plants respired all the time and produce CO2 even during the photoperiod. It's just at night any CO2 produced by the plants isn't used by the plants so hence it could tip the balance as it is the livestock blood [CO2] which drives respiration with the decreasing livestock's blood pH.
Long time since my advanced biology, I do now the ordinary level biology is well over simplified hence they teach photosynthesis during the day and respiration at night. is not until degree level that it all makes sense with those Eureka moments, well it was for me.

Edit- did a post just disappear ? As the above post was done after reading it.

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## Puntius (16 Oct 2017)

Zeus. said:


> Thought plants respired all the time and produce CO2 even during the photoperiod. It's just at night any CO2 produced by the plants isn't used by the plants so hence it could tip the balance as it is the livestock blood [CO2] which drives respiration with the decreasing livestock's blood pH.
> Long time since my advanced biology, I do now the ordinary level biology is well over simplified hence they teach photosynthesis during the day and respiration at night. is not until degree level that it all makes sense with those Eureka moments, well it was for me.
> 
> Edit- did a post just disappear ? As the above post was done after reading it.
> ...


Probably updated at the same time  

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## Zeus. (16 Oct 2017)

Puntius said:


> Probably updated at the same time
> 
> Sent from my SM-G930F using Tapatalk


Yep, mobile phones suck esp with intermittent WIFi no missing posts, I should of quoted the post OFC

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## Puntius (16 Oct 2017)

Zeus. said:


> Yep, mobile phones suck esp with intermittent WIFi no missing posts, I should of quoted the post OFC
> 
> Sent from Mountolympus via neural interface


Yeah much better doing it like that sometimes. Yes intermittent wifi causes mishaps lol... 

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## dw1305 (16 Oct 2017)

Hi all,





Zeus. said:


> It's just at night any CO2 produced by the plants isn't used by the plants


 Pretty much. 

There is a complication in that a few aquatic plants (_Isoetes, Sagittaria_) use <"CAM photosynthesis">, and there maybe others with <"more flexible photosynthetic pathways"> than had been suggested. 





> Ottelia alismoides is a constitutive C4 plant and bicarbonate user, and has facultative crassulacean acid metabolism(CAM) at low CO2.......


I don't think that CO2 builds up in the lacunae and air spaces of the plant the way that oxygen does (a lot of the oxygen used for respiration outside of the photoperiod is derived from this internal storage (this is referenced on p. 6 of <"Ecology of the Planted Aquarium">)).  The reason for this is that CO2 is much more soluble than oxygen and will tend to diffuse into the tank water.

cheers Darrel


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## Edvet (16 Oct 2017)

( I thought CAM plants are from dry arid areas only?)


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## dw1305 (16 Oct 2017)

Hi all,





Edvet said:


> I thought CAM plants are from dry arid areas only?


You would expect that, but because it works as a CO2 concentrating mechanism it looks like it is useful to plants from CO2 limited areas (submerged aquatics). My suspicion would be that if people start looking they will find that a lot more aquatic plants have unusual photosynthetic pathways.

This is from the Pedersen & Colman paper (linked above). 





> CAM photosynthesis in terrestrial plant is thought to have evolved as a trait to conserve water and is thus particularly frequent among desert plants. CAM is also present in some aquatic plants inhabiting freshwater lakes and temporary pools. Here, CAM is unimportant as a water-conserving feature and instead it is considered of adaptive importance in carbon limited environments where CO2 is stored as malate during the night and subsequently released during the day and fixed in the normal Calvin cycle. As a consequence of extensive underwater photosynthesis, CO2 drops to very low concentration during the afternoon in vegetation-rich temporary pools....


cheers Darrel


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## ceg4048 (16 Oct 2017)

Yes, agree with Darrel. There are quite a few aquatic species which evolved in CO2 poor waters or where CO2 concentration is higher at night.
I believe Vallis and Sagittaria are typical examples of CAM type plants.

Regarding the question of why it's a good idea to use less light at the beginning of the the photoperiod, the answer is simply that plants have a complex photosynthetic system and it takes time for everything to "warm up". Ramping up the light (starting low and increasing to high gradually) as opposed to bombarding them with full light just makes it easier for them to deal with the light.

Most of the problems we have with algae and poor performance in high tech tanks actually occur at the beginning of the photoperiod. Algae have very simple and efficient photosynthetic pathways and they can deal with strong lighting poor CO2 very easily. After about 4-5 hours the plants have pretty much accumulated the CO2 they need for the day, so the second half of the photoperiod is not nearly as important as the first half.

Cheers,


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## Puntius (18 Oct 2017)

Wow dude @ceg4048 thanks for your valued input. I changed my setup like this now.

Co2 start at 11h45 first light on at 14h00 then my 2nd stage lights 2 led tubes at 15h00 then lastly my one other tube around 15h45. Co2 on till 20h00 then. Airpump starts at 21h30. 2nd and 3rd tubes go off at between 21h30 and 21h40. Then last tube off at 22h15. Airpump then runs till 10 am where by that time all the co2 de gassed out. 

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