Continuous CO2 Injection - The Planted Tank Forum
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post #1 of 72 (permalink) Old 05-03-2018, 07:45 AM Thread Starter
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Continuous CO2 Injection

I have just read an article by Karen Randall. "Carbon Dioxide in Planted Freshwater Aquaria". I looked Karren up and she seems to be a very highly regarded aquarist. So I was very surprised to read, "In a properly buffered tank that is not overstocked, however, most people find that the oxygen level in the tank remains high enough, and the pH in the tank remains more stable, if the CO2 is left to run day and night without the interference of nighttime aeration."
In my experience, it takes my CO2 levels about 3 hours to go green in the drop checker. It will then gradually creep up.
Is anyone using continuous CO2? I can see the rationale that Karren points out in that it gives a more stable pH to the tank.
So I am in a quandary as to give this a go.
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post #2 of 72 (permalink) Old 05-03-2018, 11:39 AM
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I am using a pH controller linked to the CO2 solenoid valve. It only stops the injection when pH is below 6.7, otherwise, it is continuous. No problems up to now...
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post #3 of 72 (permalink) Old 05-03-2018, 12:17 PM Thread Starter
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Originally Posted by cozzuol View Post
I am using a pH controller linked to the CO2 solenoid valve. It only stops the injection when pH is below 6.7, otherwise, it is continuous. No problems up to now...
Thanks for your reply. I have not considered using a pH Controler. I would like to hear from anyone just running the CO2 overnight as well as the day.
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post #4 of 72 (permalink) Old 05-03-2018, 02:30 PM
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I am running Co2 24/7 with no issues. As my lights are in the medium PAR scale, have enough with 1,5 bps in a 30 gal. The surface skimmer provides enough surface agitation though.

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post #5 of 72 (permalink) Old 05-03-2018, 02:51 PM
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I see no problems doing this. Did it myself for a few weeks to help grow in some mosses in a shrimp tank. I set flow to drop pH by .5, which yielded about 15 ppm continuously. It helped speed things up. Most people that run DIY CO2 run it 24/7 without issue. As long as there is sufficient agitation to keep O2 levels up, you could push higher levels than I did. I was being cautious with sensitive shrimps.
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post #6 of 72 (permalink) Old 05-03-2018, 04:11 PM
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All my aquariums run CO2 and aeration 24/7, works also with 400 PAR lights.
There are number of reasons, water pH is lower and more stable, CO2 concentration is more consistent, plants can take nutrients 24/7, trace element chelating is more stable, trace element bioavailability is better, more ammonium than harmful ammonia, less equipment to worry about,


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post #7 of 72 (permalink) Old 05-03-2018, 05:24 PM
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Hi @Robert42,

Yes, Karen Randall is a highly respected and active aquarist, plant explorer (with Christel Kasselmann), aquascape judge, and on the Board or Directors for the Aquatic Gardener's Association (AGA). I run all of my tanks 24/7 with about 30ppm of CO2.
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post #8 of 72 (permalink) Old 05-03-2018, 08:34 PM
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I've run it both ways and have never observed any difference so, I figured just do it when the lights are on so I run to the CO2 store every 4 months instead of every two months. As long as your gas exchange is good, especially at night, the fish and plants will be happy.
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post #9 of 72 (permalink) Old 05-03-2018, 09:09 PM
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Quote:
Originally Posted by Seattle_Aquarist View Post
Hi @Robert42,

Yes, Karen Randall is a highly respected and active aquarist, plant explorer (with Christal Kasselmann), aquascape judge, and on the Board or Directors for the Aquatic Gardener's Association (AGA). I run all of my tanks 24/7 with about 30ppm of CO2.
Actually just want to see data proving things one way or another..
pH meters will not stop a drop in pH past the set point.
question is does nightly "natural" CO2 still decrease pH and if so by how much ect..
Keep in mind one of her qualifications is.."a well buffered aquarium"..though from the below that is most tanks (any above 1dkh).
Quote:
Myth: A Low KH results in a larger pH swing when adding CO2.
Many people are under the mistaken impression that a low KH results in large pH swings when adding CO2, while raising the KH will result in smaller pH swings. This is not the case. The KH will move the start and end pH values, but the pH swing will be the same for a given level of CO2. (note breaks down around 1dkh)
Quote:
The RATE of CO2 is what you really want to know, not a pH.
Say the tank used 50mls /300 seconds of CO2 gas.
This is entirely independent of pH/KH/Tannins, any other wonky stuff in the water that throws the pH/KH/CO2 chart off.
sorry just a reminder. Found it while looking for numbers..
https://www.plantedtank.net/forums/11...er-kh-ppm.html

Don't think it hurts either way as long as surface exchange is steady..just want real data..

Just not sure how "steady" it is though instinct tells me the swing will normally be less than off at night/on in day.........so there is that.

On a side note.. She really doesn't like non-Excel glut..

anyone want to stay up all night a record readings???

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post #10 of 72 (permalink) Old 05-03-2018, 09:59 PM
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There is no need to run CO2 at night, plants will not use it when lights are off. Tried it, no effect. Plants and fish regulate their internal pH any way so no use in keeping it stable, how stable is stable ? Not all nutrients benefit from low pH.

If you really want to keep your CO2 stable, remove all potential acid/alkaline leaching sources and get a PH controller. It may not stop the pH from going below the set point but it will stop CO2 injection when the pH drops below that. If you do not have a massive acid source or CO2 bubble this will stop the pH from going down pretty soon.

Without a pH controller you have to get extreme degassing and very high CO2 input for a stable pH. Degas enough so that plant use during the day is very small compared to your degassed amount, add enough CO2 so you get 30ppm despite the extreme degassing.

Using any of the above you will you your tank about 3x as fast. Add to this that large tank have great inertia and will not fully degas by the next day anyway. So if the drop from atmospheric equilibrium(so called "degassed") pH is 1 at lights off, you will likely get a 0.5 increase by the next day with decent aeration. So overall you have a 0.5 daily swing and no plant benefit. Worth the 3x consumption ?

I would not do it for the reasons given in the article. Fish and plants experience pH change all the time in their habitat. Lakes behave like our aquariums and get even more stratified. River water will vary greatly depending on how much rain is received upstream.

Also, many of the things in the article were debunked about 15 years ago in the hobby or just wrong. Interesting to see that AGA is proud of such an article. Speaks volumes. So I question the premise of the change. Some examples of what I am speaking about:

Quote:
In the absence of CO2, many plants have the ability to meet their carbon needs by splitting carbon
directly from carbonates in the water, which is the second method.
Actually it is a minority of the current plants in the hobby, mostly those obligate aquatic plants.

Quote:
The amount of CO2 needed in the aquarium for good plant growth is considered to be around 15 milligrams per liter (mg/L),
Most sources and plant growers go for 30 and above , but glad to see her using the correct units mg/L not ppm.

Quote:
Room air contains 1 to 3 mg/L of CO2, and aerated water dissolves only 0.7 the CO2 content of the air.
Thankfully for all terrestrial plants, air contains somewhere between 350-407mg/L, just 100x more nothing major.

Quote:
In fact, the proper use of supplemental CO2 with appropriate lighting and trace element supplementation should actually increase the levels of dissolved oxygen in the water.
We have CO2, light and trace elements. Where are the macro nutrients ? Pretty sure the O2 levels will not increase without them. Oh wait here they are:

Quote:
If the two major nutrients in the tank (nitrogen products and phosphate) are increased beyond the needs of the plants, you will experience algae problems.
Man, see told you non-limiting nutrients are a lie. Tom Barr's aquariums are full of algae with all that PO4 sitting there in water.

Quote:
However, if the water is not properly buffered, or if too much CO2 is introduced, the pH in the tank can drop quickly to levels that are lethal to fish.
Oh, pH levels and fish... Pretty sure it is the CO2 that kills them at that point. In normal aquariums, even with low KH you will not need to go lower than pH 5 with CO2 injection. If you do, you added to many other acids to the tank. Plenty of counter examples here as well of people with low KH, CO2 injection and good plant growth.

Quote:
Those aquarists with very soft water must increase the alkalinity of their water. Without the buffering properties of KH, CO2 supplementation can cause the pH to plummet, to the detriment of plants and, more especially, the fish.
Now it seems it is a must, it does not matter that in the aquarium are some fish and shrimps which need low KH. And plants seem to also be affected by low pH. Let's see... no Vallisneria still grows at a pH below 6, Egeria as well... other high pH plants in mind ?

Quote:
The goal should be to find a rate of CO2 supplementation that falls within this range, and produces a pH reading that is neutral (7.0) or slightly below
So if the water already has a pH of 7 or slightly below, the CO2 goal was achieved ??? Or if it is above 7 but fish are gasping ?
Think a better goal would be to add enough CO2 to cover the requirements of your plants under the supplied amount of light. If this is too much to keep fish alive, reduce the light intensity.
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post #11 of 72 (permalink) Old 05-04-2018, 01:46 AM
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Originally Posted by dukydaf View Post
There is no need to run CO2 at night, plants will not use it when lights are off.
Do you know of any evidence about plants not taking or using nutrients at night?


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post #12 of 72 (permalink) Old 05-04-2018, 03:02 AM
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The article indeed leaves a lot to be desired: too many absolutes and factual errors do not help author's credibility.

For me, the risks of running co2 24/7 outweight the benefits. I had too many equipment failures and plain stupidity on my part that resulted in tankfulls of dead fish.

Some of my incidents:
- over filling the tank in the evening, resulting in surface agitation change
- air wand getting clogged over time
- air tubing popping off the air pump
- air pump filter getting clogged with dust
- obstructing the air pump intake by leaving it on a wet paper towel
- running co2 at max and getting EOTD at 3 am

All avoidable and preventable for sure. I just don't trust myself without adult supervision.
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post #13 of 72 (permalink) Old 05-04-2018, 04:41 AM
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Originally Posted by Edward View Post
Do you know of any evidence about plants not taking or using nutrients at night?
Depends what nutrients you are referring to.
Last I knew (decades ago) plants do most of their real growth at night.
During the day most "growth" is just expansion of existing cells.

As to the nutrient CO2 no I suspect very little use.
Photosynthesis doesn't "stop" except at low enough light levels that zero photons are "caught"..
Conversely plant respiration (release of energy to build stuff) is continuous but increases at night due to no longer needing this energy for anything related to photosynthesis.

This is kind of fun and puts a few concepts in perspective..
https://www.quora.com/Do-plants-grow-at-night

Quote:
Plants have a mission: Catch the sunlight, convert and store the energy when you can. Grow later. During photosynthesis the plants grab all the light, carbon dioxide and water passible. With those ingredients that plant makes sugars, starches and other vital compounds.
What about plant GROWTH? Not yet. Make FOOD while the sun shines. Save cell division and elongation(growth) for the night shift.
Quote:
Indeed, plant behavior is tightly controlled by the sun. During the day, plants soak up sunlight during photosynthesis, the process they use to get energy. But when the sun goes down, plants’ opportunity to eat disappears and other physiological processes take over, including energy metabolism and growth.
Personal note, mostly related to terrestrial plants: Plant uptake of water during the day can "swell" cells so you get "growth" but not real growth (increase in cells).
Daylight increases biomass by the simple accumulation of sugars.. not by adding complex structures. All simplistic of course.
Though as you can see from above.. some things are made..

Quote:
Confuse your friends… Everyone knows that plants grow towards the light, right? Actually they don’t. The light side of the plant grows SLOWER while the dark side of the plant grows FASTER……So they are growing AWAY from the dark!
for fun.. Results are the same..

Leaving out circadian rhythms for now..

Doesn't really answer the question because it depends on which nutrients and what they are used for..
some are used in the day some at night more, some both..
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Last edited by jeffkrol; 05-04-2018 at 04:53 AM. Reason: edit
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post #14 of 72 (permalink) Old 05-04-2018, 02:18 PM
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@jeffkrol: You just shook-up my traditional thinking! My memories instantly turned to the commonly reported comments, by farmers, that they can hear the corn growing on calm nights, as the leaves move against each other. Of course, those are terrestrial plants - if that matters.

It does seem to be more an issue of circadian rhythms. One interesting comment, in one of the articles:
Quote:
Plants forced on a light cycle 12 hours out of phase didn’t do this and were thus chewed up.
which was referring to the ability of plants to put up defenses against attackers.

Hmmm …could that apply to algae formation on leaves, bringing in the whole allelopathy issue? However, another article (embedded in the UKAPS thread), claims that we can force a new circadian rhythm.

Here is what a quick Googling found:

ucsdnews.ucsd.edu/archive/newsrel/science/2011_07evening-complex.asp
https://www.popsci.com/blog-network/...o-plants-sleep
https://www.ukaps.org/forum/threads/...t-night.39891/

Biologists: correct me if I’m about to be wrong.

What do plants use to create mass? Carbon or, more correctly, sugar (cellulose and starch) made from carbon (CO2) by photosynthesis or respiration (‘burning’ O2). As I recall, they are always consuming carbon (CO2) and giving off the waste gas (O2) - day and night, but need more O2 at night. At night, O2 consumption increases because they now have to rely upon energy from ‘burning’ O2 to grow (Calvin cycle), rather than using energy from photosynthesis. Thus, the need to be sure there is plentiful O2 at night. This is respiration, which is the opposite of photosynthesis, when plants use O2 to make the sugars from the carbon rather than using light to do it but, I guess, they still use the same amount of CO2 – maybe even more just before whatever circadian rhythm “dawn” we artificially create.

This may make a case to have CO2 available all the time or, at least, come on a lot earlier than just in time to meet ‘lights on’. Would it be better to make sure that plants have access to the carbon when their growth is actually at it’s peak (before “dawn”)? An interesting experiment, which I will try in the near future, would be to run CO2 at night and turn it off during the day.

Last edited by Deanna; 05-04-2018 at 02:29 PM. Reason: edit
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post #15 of 72 (permalink) Old 05-04-2018, 03:34 PM
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Which mass?.. Cell walls are mostly complex carbohydrates which are for the most part simple sugar molecules chained together.
Plants mostly gains mass (ignoring mineral uptake for the moment) by building sugars from water and CO2. Assembly is driven (energy collected and turned to a usable form) by collecting light energy. Respiration also contributes.
We build mass by consuming mass.. and changing it. Which requires energy from respiration.

Quote:
In the primary (growing) plant cell wall, the major carbohydrates are cellulose, hemicellulose and pectin.
Proteins are built w/ amino acids so need carbon, nitrogen, sulfur ect.



Oh and chlorophyll need Mg.. It is closely related to hemoglobin w/ the main difference hemoglobin uses Iron

All "assembly" requires energy..supplied both in the photosynthesis reaction chain and respiration..

Easiest to think of this as many conveyor belts, each requiring parts and energy to start and assemble..
Which belts are moving and at what speed and what energy the assembly "people" have is determined by input and product availability.
A "supervisor" (regulatory hormones) walks around and turns some on, slows or speeds some up, or shuts some down.
Supervisors themselves are assembled somewhere based on conditions.

Carbon comes from sugars created in photosynthesis.
These "parts" are assembled into chains or split for energy.

AFAICT if no light CO2 is unnecessary since the conveyor belt that uses it is shut down.
But there is now a pile of parts for others..hopefully.

algae germinates w/ free ammonia..and doubt, though not impossible, that circ. rhythms play much of an impact..
Plant would need to produce "algaecides" based on periodicity..which is ?? to me.

Of course the complication (it's always complicated) is each "belt" can have dependencies on other belts..

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Last edited by jeffkrol; 05-04-2018 at 03:53 PM. Reason: edit
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