Does excess co2 inhibit plant growth?

Kezzab

Member
Joined
18 Jan 2016
Messages
1,105
Location
Carlisle
Hi, in my Sunday Scape journal it has been suggested that very high co2 injection could inhibit plant growth and encourage algae because it may have a detrimental effect of the tank's benefical bacteria due to creating very low ph.

Wondered whether there were any more thpughts on this?

For info its a 15l tank. Drop checker is yellow verging on clear. Water is very soft, TDS 30ish. Remineralised with pinch of TNC GH Boost and adding 1ml TNC Complete 1ml to take TDS to about 120ish. Wc is 50% daily at moment. I dont have any means of measuring ph right now.

I'm having persistent problems with soft green smothering thread like algae plus a bit of BBA and staghorn here and there.

Tank has no livestock.

Any insights?
 
Last edited:

Kezzab

Member
Joined
18 Jan 2016
Messages
1,105
Location
Carlisle
2x aquael leddy, 7hrs.

Ive had same set up in previous recent scapes with no issues...
 
Last edited:

Bryce

Member
Joined
27 Feb 2020
Messages
51
Location
Phoenix Az
Does excess co2 inhibit plant growth? No . However there is a point of diminishing returns, and that point is extremely hard to get to. Just because that same lighting worked for one tank doesn’t mean it will for another. Your algae issues are not enough co2 for the amount of light your using. Back off the light, keep co2 cranked, and keep a good fertilized water column, with good flow and things will turn around. As always a clean filter and tank is always important.
 

Bryce

Member
Joined
27 Feb 2020
Messages
51
Location
Phoenix Az
Look at the ferts if you feel the light is right. I’m not familiar with the one you’re using. Is it based on EI? I personally use heavy Co2, EI ferts, and low to low med light. I looked at your journal. No , the bacteria in your tank does nothing for algae, it does not keep it away. That’s was probably said with good intentions, but sorry flat out false. It simply breaks down waste , as I am sure you understand the cycle.
 

Kezzab

Member
Joined
18 Jan 2016
Messages
1,105
Location
Carlisle
Hi, its a complete fert, 3x recommended dose is EI equivalent and thats what im dosing.

The bacteria theory is, i think, that the high co2 leads to the tank being sort of perpetually uncycled and unstable. I can see some possible sense in that. But it seems a stretch.
K
 

Bryce

Member
Joined
27 Feb 2020
Messages
51
Location
Phoenix Az
Hi, its a complete fert, 3x recommended dose is EI equivalent and thats what im dosing.

The bacteria theory is, i think, that the high co2 leads to the tank being sort of perpetually uncycled and unstable. I can see some possible sense in that. But it seems a stretch.
K
I don’t know , your co2 level would have to astronomical . I see what your saying. I never herd of somebody co2 so high it destroys the bacteria. Even in huge body’s of water the co2 level is greater then we could ever achieve in a tank and the cycle is perfect.
 

alto

Member
Joined
24 Dec 2014
Messages
5,626
I don’t know about some of the conclusions being bandied about (how often do I get to use that phrase :p :D)
but I’m fairly certain that natural habitats with very low pH eg, 3-4 often have low plant mass - though this may just be circumstantial
(and my recollections may be wrong o_O :rolleyes: :angelic: )

But a lot of water based systems (including inside plant cells) like that “physiological pH” so if plants are expending biochemical energy maintaining cellular pH (or I’m leaping about to my own conclusions here :oops:) then plant growth will be depressed

I guess what I’m really wondering is
Why such high CO2 :confused: that the drop checker (which is a pH indicator solution) reads clear?

I can imagine that MC mat FAIL triggering considerable imbalance, in a system that was already having issues

I also read the bacteria comment as being more general re the complex “normal flora” that develops in aquatic systems
(and this goes back to those same low pH natural waters which are reported to have low levels of measurable bacteria)

Anyway I’m just rambling
:)
 

Kezzab

Member
Joined
18 Jan 2016
Messages
1,105
Location
Carlisle
Hi @alto, helpful response :)

Co2 is so high because there is no livestock so my assumption was it would help. In practice its only 1.5bps and 600grm bottle lasts 6 months coz the tank has about10ltrs water.

I think i agree thst the mc mat failing was a bigger problem, but i removrd all the rotting material and while this seems to addressed the development of bba and staghorn on the plants the fuzzy green thread stuff is still a problem.in most of the carpet.

Im currently hoping that the patches of healthy mc growth will eventually smother the stuff thats covered in algae and itll sort itself out.

I may get a ph pen just out of curiosity to see if the ph does get that low..

K
 
Joined
10 Mar 2018
Messages
454
Location
Aylesbury
What happens at night? Do you get a massive colour change.
I would do a pH profile ASAP and aim for a 1 pH drop.
Big PH swings could be giving you issues.

Other common problem is flow rate.
Have you measured your pump flow rate? I currently run over 10x and it makes a massive difference to transporting the nutrients and co2 around the tank.
I'm sure there will be plants and algae that prefer the more acidic water, some plants and algae won't do so well.
 

Zeus.

Member
Joined
1 Oct 2016
Messages
3,044
Location
Yorkshire,UK
co2 injection could inhibit plant growth
No it will boost growth - Plants in DSM thrive with 400ppm CO2, [CO2] is the limiting factor in our tanks most of the time hence we inject it.

very high co2 injection encourage algae because it may have a detrimental effect of the tank's benefical bacteria due to creating very low ph.
well your waters pH also depends on your waters dH (Hardness) to start with so tricky to anwser in a way, however with the amount of CO2 we inject I dont see it as an issue, if your using RO water neat or have very soft water and not remineralsing it then yes it could be an issue as controlling pH is very hard with RO/very soft water but it would affect the tanks inmates well before the bacteria

Check your tap water here for report ;)
 

foxfish

Member
Joined
11 Oct 2009
Messages
4,562
Location
Guernsey
I think there is a limit as to how much C02 water can hold but I can’t find an answer on the internet?
I seem to remember it being suggested that it was near impossible to get over 50ppm ?
 

dw1305

Expert
Joined
7 Apr 2008
Messages
9,983
Location
nr Bath
Hi all,
I think there is a limit as to how much C02 water can hold but I can’t find an answer on the internet?
It is a very soluble gas, so you can dissolve a huge amount in cold water. Looking at the graph you can get a theoretical maximum value of about 1500 ppm at tank temperatures and atmospheric pressure. Chart from the <"solubility of gases in water">.
solubility-co2-water.png
I seem to remember it being suggested that it was near impossible to get over 50ppm ?
I guess that is because the more CO2 you dissolve in the water the steeper the concentration gradient is between the water and the atmosphere, and the quicker it escapes. Because there is only ~ 400ppm of CO2 in the air, that gives you an equilibrium value of less than 1 ppm dissolved CO2, via Henry's law.

*I don't know how much dissolved CO2 there is in a can of coke, but <"my guess is quite a lot"> scrub that, it is an incredible amount . I've just found that coke link, which says "0.14mol CO2 in 1000mL".

The RAM of carbon (C) is 12 and of oxygen (O) = 16, and we have two of them so that is 32 and the RMM of CO2 is 12+32 = 44, 44 x 0.14 is 6.16g and mg/L is equivalent to ppm. So you have about 6160 ppm of CO2 in the can, although 0.15% (about 0.01g) of this will be dissolved carbonic acid (H2CO2) and some of the gaseous CO2 will be in the headspace of the can above the liquid.

cheers Darrel
 

foxfish

Member
Joined
11 Oct 2009
Messages
4,562
Location
Guernsey
I am sure Tom Barr wrote about this but I have searched for an hour without finding it.
I am certainly “not” sure about anything relating to this subject however it just sticks in my mind he wrote about 50ppm being a limiting factor .
Perhaps that was based on normal planted tank perimeters such as surface movement or flow rates or something else?
 
Top