Dialing in CO2 (Rubisco/light/CO2/Nutrients)

[Plants245]

Hi all!

I am not sure how technical I want to take this, but my primary question is about how we are dialing CO2 in, in the Ottawa area.

I know of some strategies. I currently determined the injection rate (considering flow and gaseous exchange) to make my CO2 concentration stable (i.e. my pH drop - cross referenced with the lime green DC and pH values), then I timed how long it took to drop my tank from off-gased pH to that amount, then just turned it on that much before the lights.

However, since light drives photosynthesis, I am wondering if we can simply increase the ramp time on a light and allow the CO2 to slowly creep up to the maximum amount - matching the CO2 to the lights the entire time.

I think that the primary reason for having CO2 stable has something to do with the requirement to create Rubisco in the plant - but I am not sure if Rubisco concentrations are light dependent or CO2 dependent.

Also, we can limit our CO2 demand by leaning our dosing regime, but I dose EI - so I want to fiddle with CO2 first.

Any thoughts? Experiences?

My tank doesn't have any issues at the moment per say; I am just wondering what other strategies work.

Primarily, I am interested because Amano didn't run as high CO2 levels as most EI users; so I know it is possible; I just do not know how.

Cheers.

[exv152]

I dial co2 based on plant growth, algae growth, and fish response. A good general rule of thumb is to drop the pH one full unit value (ex. pH of 7 to pH of 6) to reach near optimal concentrations levels.  CO2 can be reduced, but like Amano, you'd have to reduce the lights and ferts substantially, and go with low lights plants preferrably (Amano uses a lot of ferns, mosses, rotala, bolbitis, hydrocotyle, crypts, hair grass etc). A good fert regime for low lights and low co2 is PPS or PMDD. Amano's dosing regime is more inline with PPS.

[Plants245]

I dial co2 based on plant growth, algae growth, and fish response. A good general rule of thumb is to drop the pH one full unit value (ex. pH of 7 to pH of 6) to reach near optimal concentrations levels.  CO2 can be reduced, but like Amano, you'd have to reduce the lights and ferts substantially, and go with low lights plants preferrably (Amano uses a lot of ferns, mosses, rotala, bolbitis, hydrocotyle, crypts, hair grass etc). A good fert regime for low lights and low co2 is PPS or PMDD. Amano's dosing regime is more inline with PPS.

How do you do it exactly? Do you just arbitrarily turn on CO2 1 hour before lights and then just watch, ignoring all measurements including stability? I think this is the way to go to be honest; I just haven't tried to do it - but I'd like to. Please share .

Amano's substrate is quite nutrient rich (and I have not read enough on PPS or PMDD substrates to know if they advise an inert or active substrate - please correct me because I do not know), albeit a leanish water column dose; PMDD allows you to dictate your tank via make your limiting nutrient the phosphate dose (since phosphate is much more mobile in the plant tissue rather than out of) instead of CO2 ... which is actually kind of cool and I'd like to try it - could you run a high light with this? And if not, why?

In terms of lighting,  I think Barr measured ADA gallery at around 40ish micro mol ... moderate light - https://barrreport.com/threads/ada-lighting-at-aqua-forest-and-nice-low-par-values-who-knew.4865/ -  (which is what EI calls for as well - in fact, I think Barr advocates a starting point of 40mmol for most people) - I also saw ADA scapes with Wallichi which I've read (since I have not grown) requires higher light and co2.

I watched a video where Barr said that you just turn on the CO2, then watch your fish - kind of as you suggest - then turn it up a bit more and so on -- I have never heard Amano talk about CO2.

The Drop checker method and pH profile seem to be common through Europe aside from big names like Filipe and Green Aqua (who again do not talk about dialing in CO2) ... I think it is reserved for master classes  -- other than that some of the big names that I see use ADA system - which I have no experience with.

In any case, I would greatly appreciate some more details on your strategy .

[lucius]

I did what exv152 did and just played with my CO2 until I got one pH unit drop from lights on to lights off.  I used a pH controller for this or you could also use a pH probe and take the readings twice a day.  I also splurged a bit and bought Hoke Milli-Mite needle valves.  They have indicators on the knob and it's way easier to adjust the needle valve when you have a point of reference.

[Plants245]

I did what exv152 did and just played with my CO2 until I got one pH unit drop from lights on to lights off.  I used a pH controller for this or you could also use a pH probe and take the readings twice a day.  I also splurged a bit and bought Hoke Milli-Mite needle valves.  They have indicators on the knob and it's way easier to adjust the needle valve when you have a point of reference.

Hi Lucius! Thanks for the reply.

So your concentration of CO2 reaches its peak ppm at the end of the light cycle? Presumably it turns on an hour before the lights? Or do you turn it on at lights on?

Do you EI dose with this as well, or do you employ a leaner dosing regime?

I will look into those Hoke Mili-Mite needle valves. Currently, I have the Milwaukee; however, once I realized that I can ignore the needle valve and just spin the black knob, I am quite satisfied with it.

[exv152]

Like Lucius, I use a pH controller which cuts off the co2 once the pH reaches its target (of one full unit drop). This is my strategy and it has produced great results consistently for the past 4-5 years on a 125g. There is no guess work when you use a controller system. I don't recommend it for everyone because it's not cheap, but there are many pH controller options out there. This has allowed me to dial everything in along with high light and PPS fertilizer dosing. I also invested in ADA amazona substrate, which in my opinion has been just as important as the lights, co2 and ferts.

[Plants245]

Like Lucius, I use a pH controller which cuts off the co2 once the pH reaches its target (of one full unit drop). This is my strategy and it has produced great results consistently for the past 4-5 years on a 125g. There is no guess work when you use a controller system. I don't recommend it for everyone because it's not cheap, but there are many pH controller options out there. This has allowed me to dial everything in along with high light and PPS fertilizer dosing. I also invested in ADA amazona substrate, which in my opinion has been just as important as the lights, co2 and ferts.

Does your controller run all day? Or just during a time frame that you have laid out? For example, do you say at 2 hours before lights, engage the pH controller, the pH controller drops your pH to a certain amount BEFORE lights on, then lights on .... keep it stable .... then cut it off with the timer.

Or, do you just let the pH controller open and close the solenoid, engaging CO2, as it pleases - maintaining your target pH forever i.e. your target CO2 day and night?

[Plants245]

Lucius + @exv152,

The one concern I'd have with the pH controller would be from non-inert rocks hardening the water and/or the natural acidification of our tanks from ... everything (including but not limited to the nitrogen cycle and the substrate) . This could give a discrepancy between water changes and so over a week your plants would experience different"ish" CO2 levels - increasing or decreasing the demand for RuBisCo creation ... in any case, I do not think it is so important because if you use the strategy from day 1, you can just learn the tank to get the drop you need.

What I am wondering is if you tailor that drop prior to lights on or not -- or if you let the controller run it all day (in this case, I think your target would be before lights on).

[lucius]

The pH controller has a power socket that I plug in between a timer and my CO2 solenoid.  On the pH controller, I set it (after a ton of tinkering) to my desired low and high levels.  One hour before lights on, the timer goes on, this provides power to the power socket and turns on my solenoid.  Then one hour before lights off, the timer goes off, the power socket loses power and the solenoid goes off.  Between the timer going on and off, the pH drops one unit.  If the pH drops one unit before the timer goes off, then the pH controller will shut off and turns off the solenoid.

I worry about nothing else.

[exv152]

I run a Neptune Apex controller. The controller also controls the lights, co2, monitors temperature, runs the autofeeder etc etc. The co2 operates freely between a preset time schedule set in the controller programming, and it goes on and off at will to maintain your target pH. The Apex is nice too because you can run reports in the form of graphs that provide a visual aid as to when your lights are coming on and when the co2 is hitting its target, and you can tweak it accordingly. Leaving very little to chance. That said, any controller will do just as good a job. Before the Apex I used to run a Milwaukee pH controller set on a designated timer, and the lights on a separate timer set to come on 1 hour before the lights come on, which also worked quite well.

[Plants245]

Thanks for the replies!

Lucius, how did you determine the 1 hour benchmark for before lights on time? And do you notice (just by observation) if your pH hits your target before the lights on? Or does it merely have a gradual drop throughout the photoperiod?

exv153 - I like that! Apex + automation! Have you done this with an EI style dosing and/or minimal water change schedule (I am assuming you are changing 50% ish a week?). Does the controller still do the trick?


So it seems many are using a pH controller to monitor a particular drop.

Does anyone dial CO2 without the use of a pH controller? If so, what strategy?

Loving the conversation friends!

Cheers.

[lucius]

I just tested and played with my settings until I got what I want.  I never noticed how much it drops at lights on.

[exv152]

I used to do EI dosing years ago, but I have moved away from a heavy dosing regime in favour of a more moderate regime (PPS or the perpetual preservation system) and less water changes (20-30%). The TDS of the tank water tells me when it's time to do a water change, and how much to change.