Proper use of CO2

[Zulato]

Hi all,
I know all of you are tired of answering those questions but I want to explain my case:

About 1,5 years ago I started a new tank - 250L (ish) with an Oase biomaster thermal 600 (initially 850) . My plan was to have the dreams planted aquarium as I’ve had many small successful planted tanks before … so I got a nice CO2 setup and then I started to struggle… well, first of all I could never have a good distribution of CO2 throughout my tank, secondly my DC never read anything different than Green (I set it far from the diffuser to make sure that there was CO2 all over but I don’t think the reading was right ) And thirdly, my plants never grew healthily…

Eventually I gave up, let the CO2 run as it was , continued using the fertilisers and only the strong and easy plants throve.

Now I decided that I want to re scape it and do the right thing this time (starting this week) and please I need the good help of you with the following:

What is a good diffuser to use and what type (in-line, reactor, in tank…)

How can I make sure I get CO2 all over the tank (my filter doesn’t have a fantastic flow) . Should I use another pump inside the tank to help?

My tap parameters are roughly ph 7.4 and dKH 2 which I bring it up to 4 with aquadur

Is the method of ph drop reliable ? Measuring ph at lights on and lights off ?

Sorry for so many question and much appreciated for any help 😊

 

[foxfish]

If you are still using a 250l tank then a single in tank diffuser is going to struggle but my best advice is dont stock any fish until you have the C02 on song…..

 

[Corbie]

Not cheap but I like, and use, the "pro" version from co2supermarket. You can add several diffusers to it and can control each one separately. I use it with 600g welders' CO2 cylinders which I can get from any tool / diy store.

 

[erwin123]

Is the method of ph drop reliable ? Measuring ph at lights on and lights off ?

Ideally, the difference in pH at lights on versus lights off should be no more than 0.1 (i.e. stable pH during photoperiod).

 

[Zulato]

If you are still using a 250l tank then a single in tank diffuser is going to struggle but my best advice is dont stock any fish until you have the C02 on song…..

Thanks for your reply. In my case it won’t be possible as I’m redoing my tank so I have to temporarily move all my fish to another tank then back as I don’t have much space in my apt and already have 2 tanks running !
My CO2 regulator has 2 outlets so maybe I could use both in the same tank In different locations?

 

[Zulato]

Not cheap but I like, and use, the "pro" version from co2supermarket. You can add several diffusers to it and can control each one separately. I use it with 600g welders' CO2 cylinders which I can get from any tool / diy store.

You actually gave me a good idea as I haven’t thought about it before. My CO2 regulator has 2 out so I can use both in different locations of the tank maybe

 

[Zulato]

Ideally, the difference in pH at lights on versus lights off should be no more than 0.1 (i.e. stable pH during photoperiod).

But that’s very hard to get initially isn’t it? From what I read in this forum ( correct me please if I’m wrong) , when I inject CO2 the oh will start dropping and if I have a normal ph of around 7 and kh of 4 if the drop is around 1ph that means I’m injecting around 30ppm? Is that right ?

 

[pat1cp]

How can I make sure I get CO2 all over the tank (my filter doesn’t have a fantastic flow) .

Is a cheap 2nd filter an option?

 

[Zulato]

Is a cheap 2nd filter an option?

Well it would be if I had space in the cabinet. I though of getting one of those : Small pump just above the diffuser so it would help with the flow and spread the CO2 a bit better . Would it be a good idea?

 

[Zeus.]

Oase biomaster thermal 600

So 1250LPH output which yields 'x5 filter output to tank ratio - ideally x10 would be better, however folk do manage with x5 ratio but everything needs to be optimised
How much and what type of media do you have in there? fine media and ceramics have a but hit on filter output and are not needed in planted tanks- Bio Media
What outputs are you using? I found using a spray bar with smaller outputs reduced the filter output However it produced powerful jets of water which generated better flow in the tank when the spay bar was set correctly. 'Flow/tank turnover is King' in the tank - what generates it is irrelevant but setting the Flow generates can be tricky as they need to work together. a Spray bar along the back of the tank can work very well as well as twin lily pies for open top tank

Duel stage regulators can also help as you can increase the working pressure which increases the CO2 injected via the atomiser. CO2 reactors Help also IMO/IME (plus bubble free tank except for pearling) and they don't need high flow rates though them to work well either IME, high flow rates can increase how well CO2 reactors work but there comes the noise of the swirling water which I am not a fan off.

 

[erwin123]

But that’s very hard to get initially isn’t it? From what I read in this forum ( correct me please if I’m wrong) , when I inject CO2 the oh will start dropping and if I have a normal ph of around 7 and kh of 4 if the drop is around 1ph that means I’m injecting around 30ppm? Is that right ?

The CO2 should stop dropping if you have tuned it correctly. While we are injecting CO2, we are also losing CO2 by gas exchange with the surface, and CO2 is being used by the plants. Coincidentally, I was doing a pH profile today because I bought a new pH meter from amazon (Apera PH60):

• 24hr Degassed pH 7.25
• 2pm CO2 on (didn't record pH)
• 4pm lights on pH 6.22
• 5pm pH 6.18
• 6.30pm pH 6.13
• 7.45pm pH 6.13
• 9.00pm pH 6.10
• 9.50pm CO2 off pH 6.11

I get a1.0 pH drop on lights on, but it keeps dropping and somewhat stabilises about 3 hours after lights on with a 1.1pH drop, which is not 'perfect' but 'good enough'.

However, I'm increasing my light intensity to try to turn my Rotalas pink (either that or crash the tank), so I probably need to increase CO2 to match the increased light, maybe a 1.1-1.2 drop.

(Edit: added - latest 9.00pm/9.50pm readings) 6.10-.6.13 probably within the margin of measurement error for the meter.

 

[Zeus.]

2pm CO2 on (didn't record pH)

Irrelevant as you already have Degas pH

• 4pm lights on pH 6.22
• 5pm pH 6.18
• 6.30pm pH 6.13
• 7.45pm pH 6.13

Which isn't bad at all, I do prefer to get it less than 0.1 drift in pH, but it is closer to 0.1 drift than 0.2

Remember although we talk about a 1.0pH drop as ideal which yields approx. 30ppm CO2. For stability of the tank and to prevent CO2 related issues the pH drop or [CO2] is irrelevant - its the stable pH from lights on till CO2 off that's important - details in Clives (Aka ceg4048) post below

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.

 

[Zulato]

So 1250LPH output which yields 'x5 filter output to tank ratio - ideally x10 would be better, however folk do manage with x5 ratio but everything needs to be optimised
How much and what type of media do you have in there? fine media and ceramics have a but hit on filter output and are not needed in planted tanks- Bio Media
What outputs are you using? I found using a spray bar with smaller outputs reduced the filter output However it produced powerful jets of water which generated better flow in the tank when the spay bar was set correctly. 'Flow/tank turnover is King' in the tank - what generates it is irrelevant but setting the Flow generates can be tricky as they need to work together. a Spray bar along the back of the tank can work very well as well as twin lily pies for open top tank

Duel stage regulators can also help as you can increase the working pressure which increases the CO2 injected via the atomiser. CO2 reactors Help also IMO/IME (plus bubble free tank except for pearling) and they don't need high flow rates though them to work well either IME, high flow rates can increase how well CO2 reactors work but there comes the noise of the swirling water which I am not a fan off.

Hi there. I have 2 of bio filter and all the others are mechanical filtration. But even running it empty the flow is not great. It’s something to do with the oase filter . And output I’m using the original one it’s like a lily pipe but smaller and doesn’t go down as much.

 

[arcturus]

Hi there. I have 2 of bio filter and all the others are mechanical filtration. But even running it empty the flow is not great. It’s something to do with the oase filter . And output I’m using the original one it’s like a lily pipe but smaller and doesn’t go down as much.

You can improve the flow of the Oase BioMaster by <tweaking the pre-filter pipe>.

Add a circulation power head to the tank. The flow of just one BioMaster 600 is the bare minimum for a 250 l tank with CO2 injection. Or get a second filter. Ideally, replace the CO2 diffusor with an external CO2 reactor to maximize dissolution. The reactor will be quite noisy if the water flow is high. You can overcome this issue with a bypass around the reactor (see example in the photo).

 

[Zulato]

You can improve the flow of the Oase BioMaster by <tweaking the pre-filter pipe>.

Add a circulation power head to the tank. The flow of just one BioMaster 600 is the bare minimum for a 250 l tank with CO2 injection. Or get a second filter. Ideally, replace the CO2 diffusor with an external CO2 reactor to maximize dissolution. The reactor will be quite noisy if the water flow is high. You can overcome this issue with a bypass around the reactor (see example in the photo).

View attachment 178408

That’s something of great help! Thanks mate … not sure if I’ll have space for all of that tho …

 

[arcturus]

That’s something of great help! Thanks mate … not sure if I’ll have space for all of that tho …

If you have a 250 l tank (likely 100-120 cm wide) you should have a wide enough cabinet for the setup. The reactor in that pic has a ~10cm diameter and ~20cm height, ~40cm height including the bypass pipe. You should be able to fit a similar reactor behind the filter or CO2 cylinder. IMO, a decent CO2 reactor is a good investment. It not only dissolves CO2 better than an inline or in-tank diffuser, but also requires near zero maintenance.

 

[Luciën]

View attachment 178408

That's a reactor I've never seen before, how does it work or are there photos from the inside? It seems rather small for a conventional reactor.

 

[arcturus]

That's a reactor I've never seen before, how does it work or are there photos from the inside? It seems rather small for a conventional reactor.

JDAquatec - STARTSEITE

Vorsprung durch Ideen

www.jdaquatec.de

There was a picture of the inside of the reactor but it seems it is not available anymore. There is a kind of spiral around the inside of reactor that creates a water vortex. You can get full CO2 dissolution even with the CO2 needle valve cranked up...

PS: this is not mass-produced but handmade... you can get one through e-bay.