How many hours co2

[Becksy]

Good evenin, I’ve just got my tank up and running with plants. No fish. I’m having my light on for 6 hours. How many hours should I have the co2 on please. And do I have co2 come on before light. Any thanks.

 

[Konrad Michalski]

When your light turns on your drop checker
needs to be lime green colour. It usually takes 1-1.5 hour. I would turn co2 off around an hour before light goes off.


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[Becksy]

When your light turns on your drop checker
needs to be lime green colour. It usually takes 1-1.5 hour. I would turn co2 off around an hour before light goes off.


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Thank you. I’m waiting for my drop checker to come tomorrow hopefully. So I’m guess co2 to come on one hour before light are on and an hour before lights off?

 

[Konrad Michalski]

It’s all just a guess. If you have big water circulation in your tank with water surface being disturbed you may need to inject more co2 but it will reach the right level quicker. If water circulation ain’t big it may take two hours or longer for your drop checker to reach lime green colour. Just start with an hour and experiment it.


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[Stu1407]

I have my C02 turn on two hours before lights on and going off one hour before lights off. My checker is normally lime green at the end of two hours but keep an eye on your fish when you first start to make sure you aren't poisoning them. Where you position the diffuser is also important. Normally on the opposite side of the tank to your inlet pipe or in my case a Nero 5 turned down so that it creates a circulation that pushes the C02 bubbles along the substrate as they rise towards the surface. Try to do this in an area that is clear and allows for good circulation. If you have a look on here there is a lot of excellent advice re C02 but also the 2hr Aquarist site is worth a look.

 

[Hanuman]

If you want to have a more accurate way to know how much CO2 is in your tank and how much you need, I would recommend you to measure your PH when water is degassed and aim for 1 PH drop from that after CO2 has been on for about an hour. Make sure you have proper surface agitation and water circulation in the tank. Surface skimmers are in my opinion a must have as you bring highly oxygenated water to the lower parts of the tanks while also allowing a better gas exchange by making the surface clear of any biofilm that could build up.

 

[Zeus.]

For CO2 injection to work well without the many CO2 injection related issues you need-
Good flow/tank turnover
A stable [CO2]/pH from lights on till CO2 off
Time to get the injection rate right to suit your tank.

Getting it wrong first time is normal

 

[Becksy]

It’s all just a guess. If you have big water circulation in your tank with water surface being disturbed you may need to inject more co2 but it will reach the right level quicker. If water circulation ain’t big it may take two hours or longer for your drop checker to reach lime green colour. Just start with an hour and experiment it.


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Ok thank you very much. When I get my drop checker I’ll do as you’ve advised.

 

[Becksy]

If you want to have a more accurate way to know how much CO2 is in your tank and how much you need, I would recommend you to measure your PH when water is degassed and aim for 1 PH drop from that after CO2 has been on for about an hour. Make sure you have proper surface agitation and water circulation in the tank. Surface skimmers are in my opinion a must have as you bring highly oxygenated water to the lower parts of the tanks while also allowing a better gas exchange by making the surface clear of any biofilm that could build up.

So if I’m reading you right I need to check the ph of the water when the co2 hasn’t been on. And what ph should my water be? I messaged it yesterday while gassed and it was between 6.5 and 7 Should I do the test before the co2 comes on? If so what should my ph be? Sorry for dum questions.

 

[Becksy]

For CO2 injection to work well without the many CO2 injection related issues you need-
Good flow/tank turnover
A stable [CO2]/pH from lights on till CO2 off
Time to get the injection rate right to suit your tank.

Getting it wrong first time is normal

Ok brilliant, I’ve got good flow within the tank and the surface of the water is broken with the Lilly a little out of the water. So I’ll measure the ph from when the lights go on to coming off. and I need a consistent ph Correct?

 

[Zeus.]

Ideally it is best to do a pH profile.
Take pH from pre CO2 on time every 30 mins till lights off and pH when lights come on.
We are after as little pH drift as possible from lights on till CO2 off - I personally aim for less than 0.1pH drift - which is hard to achieve
the reasons for this stable pH are -

We have a fairly well grounded, basic understanding of the photosynthetic processes.
A. We understand that Rubisco's job is to capture CO2 molecules and to deliver the molecules to the Calvin Cycle reaction centers. We know that Rubisco is hugely expensive and consumes a lot of resources to produce and to maintain. In low tech tanks, where the CO2 concentration is low there is a much higher density of Rubisco in the leaf because you need more of the protein to capture the small amounts of CO2. In gas injected tanks, the Rubisco density in the leaf is lower.

B. We also know that during Calvin Cycle, the fixing of Carbon involves some intermediate carbohydrate products until the final product is a type of glucose.

So, for item A. we know that when the plant senses that high concentrations of CO2 is available, it responds by reducing the production of expensive Rubisco. When it senses a lower CO2 concentration it must increase Rubisco production, however because this protein is so complicated and heavy, the increased production requires 2-3 weeks in order to change the density in the leaf to match the new gas concentration level. So it is much easier to reduce production than it is to increase production. When increasing gas injection therefore, it hardly takes any time to see an improvement in health. When lowering the concentration, the plant will suffer because it must now ramp up Rubisco production to account for the loss of CO2 availability.

When increasing the light, the plant must reallocate resources from Rubisco production/maintenance in order to deal with the increased radiation. This may entail new pigment production for protection. When the light is reduced, the plant then reallocates the light gathering proteins and can devote them to Rubisco production/maintenance.

So when we mess around with light and gas, we have some degree of predictability.

 

[Hanuman]

So if I’m reading you right I need to check the ph of the water when the co2 hasn’t been on.

Correct. You could even take a small cup of water from the tank and let it degas for 24h. Take a reading. From that reading target a 1PH drop. Ideally that drop should occur within 1 hour of the CO2 having been on and before lights turn on so that water is saturated with CO2. Plants use/need the most CO2 at the beginning of their photosynthetic period.
As a rule of thumb 1PH drop ~ 30ppm of CO2.

And what ph should my water be?

Doesn't matter what it should be. It will be what the PH meter will indicate you what it is. Most probably your PH will be around PH6.5/7 if you are using an active soil.

Ideally it is best to do a pH profile.
Take pH from pre CO2 on time every 30 mins till lights off and pH when lights come on.
We are after as little pH drift as possible from lights on till CO2 off - I personally aim for less than 0.1pH drift - which is hard to achieve
the reasons for this stable pH are -

Yes that's the ideal thing to do. However, making a CO2 profile is much easier done when you have a PH probe with a logger. Obviously one can use a PH pen but it's just such a pain specially because these pens are always drifting. They can provide a general idea though which is a good starting point.

 

[Becksy]

Thank you everyone for all your wisdom.