How to manage CO2 overnight - The Planted Tank Forum
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post #1 of 40 (permalink) Old 09-03-2019, 12:28 AM Thread Starter
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How to manage CO2 overnight

Hey guys, so I recently got a second tank and suddenly dosing thrive is no longer economically sound. I just got a DIY CO2 reactor, and am currently running it in my 10 gallon but plant on splitting it between my 10 and 15 gallon aquariums.

This sounds dumb, but I am confused as to how you can balance the CO2 when your lights go out at night and the CO2 is no longer used. If I turn the CO2 off at night, then the CO2 will drop rather quickly back to nearly 0 by morning. I know this because my well water has about 30 ppm CO2 and within a night after a water change, my pH is high again. In the morning, I would then have to turn the CO2 up high in order to make the buildup back to 30 ppm, then lower it in order to maintain.


I'm now considering running an aerator on a timer to control it. Could I run that all night, and then at some point before the lights come on, have it turn off in order to buildup the CO2 again? Is that the best method for balancing? That or basically the same thing, but with a solenoid instead.
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post #2 of 40 (permalink) Old 09-03-2019, 12:37 AM
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Originally Posted by Jah410 View Post
Hey guys, so I recently got a second tank and suddenly dosing thrive is no longer economically sound. I just got a DIY CO2 reactor, and am currently running it in my 10 gallon but plant on splitting it between my 10 and 15 gallon aquariums.
What doses dosing Thrive have to do with the CO2, or have I missed something???

Most turn on CO2 1-2 hours before lights on and turn off during the last hour of photo-period.

Could be a solenoid for each tank or both are on the same schedule.

Each tank will need some form of flow control even if sharing the same CO2 manifold.


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post #3 of 40 (permalink) Old 09-03-2019, 12:53 AM Thread Starter
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Oh I'm sorry meant excel, not thrive. And so basically what I outlined except with a solenoid control? I would then have a split valve after the solenoid in order to split the stream. Then two control valves, one on each split. That all sound correct?
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post #4 of 40 (permalink) Old 09-03-2019, 01:30 AM
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Some things to consider;

- If you are injecting CO2, you aren't likely to noticeably benefit from Excel. So, you can cut it out and save some money.

- I started my CO2 as soon as ambient light entered the room, but an hour before is fine, too. However, I recently switched to 24/7 CO2, but with reduced CO2 levels (~40ppm down to ~30ppm). I plan to go lower if all holds up. My thinking is that plants uptake NH4 24/7, so they will benefit by having the CO2 at night. Plus, I dose NH4 around the clock. CO2 will build higher at night and start the day at much higher levels (before being consumed), but that is also what happens in nature.
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post #5 of 40 (permalink) Old 09-03-2019, 10:02 AM
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If by diy co2 you mean yeast and sugar, I doubt you will make enough co2 to worry. If you are worried, you can run an airstone at night and it should help gas it off. If you mean pressurized co2, put it on a timer to turn off an hr before your lights go out.
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post #6 of 40 (permalink) Old 09-03-2019, 03:37 PM Thread Starter
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Yes I'm forgoing the use of excel now that I have the system. I decided to get co2 because it's a more economical system now that I have more than 1 tank.

I use a sodium bicarbonate and citric acid reactor to get my co2. I was actually surprised by the ammount it produces. I have relatively slow growing plants mostly, SR is carpeting the tank and is my largest plant by volume contributor, but also some Java moss, water wisteria, and ludwigia. I need the reactor running at something like 10 bpm to get around 30ppm co2 and maintain it. Maybe that changes as the plants become adapted to it though. I think leaving it on overnight may lead to poisoning.
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post #7 of 40 (permalink) Old 09-03-2019, 07:07 PM
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However, I recently switched to 24/7 CO2, but with reduced CO2 levels (~40ppm down to ~30ppm). I plan to go lower if all holds up. My thinking is that plants uptake NH4 24/7, so they will benefit by having the CO2 at night. Plus, I dose NH4 around the clock. CO2 will build higher at night and start the day at much higher levels (before being consumed), but that is also what happens in nature.
If CO2 goes up at night then there is not enough aeration. I can have pH drop 1.6 pH solid stable 24 hours a day with proper aeration. It works as equilibrium CO2 <=> Aeration, without plants affecting it.


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post #8 of 40 (permalink) Old 09-04-2019, 12:59 AM
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If CO2 goes up at night then there is not enough aeration. I can have pH drop 1.6 pH solid stable 24 hours a day with proper aeration. It works as equilibrium CO2 <=> Aeration, without plants affecting it.
I considered driving it off with more aeration but, if the fish are ok, why bother? If it were a problem, rather than drive it off, why not just do the inverse and shut the CO2 off at the point where a noticeable increase registers?
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post #9 of 40 (permalink) Old 09-04-2019, 02:55 AM
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Quote:
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If CO2 goes up at night then there is not enough aeration. I can have pH drop 1.6 pH solid stable 24 hours a day with proper aeration. It works as equilibrium CO2 <=> Aeration, without plants affecting it.
CO2 going up at night is natural, at least in a soil substrate with lots of plants. I watch my pH drop every night, and every siesta.

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post #10 of 40 (permalink) Old 09-04-2019, 03:05 AM
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Lots of people run CO2 24/7 as I do. My ph does not drop significantly more at lights off to worry about it (maybe 0.05-0.1 max). I dont run an airstone or wavemaker but I do have a surface skimmer which helps with Aeration.


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post #11 of 40 (permalink) Old 09-04-2019, 03:09 AM
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CO2 going up at night is natural, at least in a soil substrate with lots of plants. I watch my pH drop every night, and every siesta.

Cheers
Are you injecting pressurized CO2 24/7 to 1.6 pH drop with no controller?

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I considered driving it off with more aeration but, if the fish are ok, why bother? If it were a problem, rather than drive it off, why not just do the inverse and shut the CO2 off at the point where a noticeable increase registers?
Because when you see CO2 increase at night the system is fragile and can harm fauna when something goes wrong. We are talking about 24/7 injection and no controller here so not to confuse soil set ups.


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post #12 of 40 (permalink) Old 09-04-2019, 03:23 AM
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I am monitoring with my Neptune Apex EL, but not currently adding CO2 or fertilizers. I tried the cheap Fluval kit, but just for a bit. I do occasionally add a little Easy Green.

I know there are so many approaches to planted tanks. I do IT for a living, so I go for autopilot tanks. I don't want to learn dosing or weekly water changes. I want everything to live easily.
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post #13 of 40 (permalink) Old 09-04-2019, 03:29 AM
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Nice, can you share some Neptune Apex EL monitoring results?


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post #14 of 40 (permalink) Old 09-04-2019, 03:35 AM
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Here is a screenshot. I don't claim to be conducting science. Sometimes I leave my window open, and sometimes I change my AC settings. The tank is much more boring.

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post #15 of 40 (permalink) Old 09-04-2019, 03:40 AM
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Because when you see CO2 increase at night the system is fragile and can harm fauna when something goes wrong. We are talking about 24/7 injection and no controller here so not to confuse soil set ups.
Yes: I have no pH controller and have an inert substrate. CO2 has to rise, at night, without mitigation, but I don't see evidence of any harm to the fish (no gasping behaviors). I'm similar to @cl3537 where I've logged a maximum .1 point shift in pH. So, maybe up to 10ppm additional CO2. It's not a tolerance issue with the meter, as the pattern is persistent.
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