Controlled CO2 experiment

Hello all, the chart below is very interesting for anyone that is running or contemplating running a planted aquarium with pressurised CO2 injection.

Basically the chart is important because it illustrates the effects of when CO2 is switched on to when it is switched off again. Now you may say why is this important, well 90% of algae issues in highlight planted tanks can be attributed to CO2 issues and (usually low or flucuating unstable levels) this chart clearly shows what best user practise should be for you and me to get the best results.

The chart is broken into 48 x 1/2 hr segemts to represent a 24hr period. The chart illustrates how long it takes for the CO2 to become stable in a planted aquarium and this is the key point, it takes a lot longer than most people think. Also when you switch the CO2 off you can see the almost immeadiate dropoff in CO2 levels, this is also important as you often hear of people who presume that CO2 will stay in the water column a lot longer than it actually does and who presume it is ok to switch off the CO2 before the end of the lighting period, this is a bad idea, the CO2 should stay on right until the end of the light period.

So basically to sum up you need to switch the timer for your solenoid to the 'on' position 5 hrs before lights on and run the CO2 right until the end of the light period. Doing this will give you the most stable results running your CO2 and therefore in theory should minimise any algae issues you may encounter.

This experiment was carried out under labatory conditions by Mr Tom Barr who is a scientist and university lecturer in the USA, he is also considered to be the leading scientific expert in planted aquariums worldwide. The excellent chart below is also attributed to him.



Anyway hope that helps food for thought anyway.

Peter

Hi Peter,

Very intresting report. I imagine it will lead to alot of amendments in text that provide for CO2 to be knocked on with lights. Correct me if I read the graph wrong but is it between the 6 and a half to seventh hour before CO2 ppm starts to increase? So when photosysnthesis is at its highest rate there is the highest/stable levels of CO2 to maximise photosynthesis. Even at the maximum rate of photosynthesis CO2 levels are maintained through at 40ppm? Did it give the dosage of CO2 to achieve this ? Would the fact that CO2 is being pumped in for 5 hours before lights on cause a pH swing? How would you suggest would be a rough guide to dosage?

Cant wait to see the results you get in your tanks. Even though I find it will be hard for you to improve on perfection


Cheers
Alan

Zoom wrote:

Hi Peter,

Very intresting report. I imagine it will lead to alot of amendments in text that provide for CO2 to be knocked on with lights. Correct me if I read the graph wrong but is it between the 6 and a half to seventh hour before CO2 ppm starts to increase? So when photosysnthesis is at its highest rate there is the highest/stable levels of CO2 to maximise photosynthesis. Even at the maximum rate of photosynthesis CO2 levels are maintained through at 40ppm? Did it give the dosage of CO2 to achieve this ? Would the fact that CO2 is being pumped in for 5 hours before lights on cause a pH swing? How would you suggest would be a rough guide to dosage?

Cant wait to see the results you get in your tanks. Even though I find it will be hard for you to improve on perfection


Cheers
Alan

Hi Alan, Im not sure what parameters were used for the experiment tbh. I know it was done under lab conditions with expensive equipment that is way beyond the reach of the average hobbyist. A lot of Toms research you have to pay for but it usually makes it into the mainstream sooner rather than later anyway so I dont pay basically.

The research is new to me as well, up to this I would always switch the CO2 on 2-3 hours before lights on and let it run right through the light period until lights off, but this clearly isnt enough. So I have amended that and am going to do at least a 5 hour lead in time from now on. I dont think it really matters what dosage rate (bubble rate)that he used because there is a maximum rate that you cant go beyond anyway without gassing the fish so thats going to be your max and you cant go beyond that. So we could start off at one buble per second and build it up slowly, 2 bubbles 3 bubbles etc, and build it up to find the correct rate for your size tank, just like you normally would.

But yes you are correct in that between 6 1/2 and 7 hours is the optimum point in the experiment but I think at that stage he is in the zone anyway and the swings are levelling out. I think the main point to take from this is that you need a long lead in time rather than a short lead in time to get the CO2 levels up to the required levels and dont switch off the CO2 until the lights are switched off. Even if your dropchecker is showing lime green after a couple of hours I would still do the longer lead in time basically to get to more stable levels. Should be no problems with PH swings that you dont normally encounter. You could try it at 5 hours and this may work for you thats where I have mine set for now and it seems to be working for me so far, early days though. I think if you are having any problems with algae this could be a good place to start.

I have only one potiential competition tank going right now, Im not sure where its going though tbh, not where I wanted it to go anyway, it started off as one thing and has ended up as another! but still working on it so we will see where this one ends up.

Cheers Alan

Peter

Thanks for the info , I have tried Tom Barrs E.I method before and was very unsuccesfull, maybe the tank was too large to dose properly I think I'll have to start small and work my way up , jumping in at the deep end again.
I'm going to be setting up a new planted tank soon , and this is something I'll have a look at, nice project to try to see the results. My problem Is I'm always tempted to over stock the tank after It is planted up nice and everything going well. One Day I hope to get something that I could say would be worthy of a competition (I'll Keep trying ).
Good luck with the competition tank, your doing us all proud here in Ireland putting us on the map, Be nice to see someone starting a shop to provide plants at competitive prices and the accesories to go with it opposed to having to search online. Trying to get my hands on ADA products and it is a nightmare in shipping costs. If we were able to source things here it might entice more people into the aquascaping arena.

Keep up the good work
Alan.

Very interesting. I have altered my timers for Co2 to come on 6 hours before lights.
I should mention there is no fish in the tank.

If i get around to it i will set up a PH monitor tomorrow to see the changes in PH and in a few days post the results.
This will be very basic but it might give a rough idea of when the PH changes and by how much.
Something worth knowing if you keep fish in the tank.

great thread peter, alan and darren. it is posts like this that inspire the rest of us to take an interest in planted tanks.

Wen are you starting your first planted tank Derek?

I have some spare equipment if needed;)

still researching.

Darren thats Great , I'll follow this project as I'm going to have a go too without fish. I'll be starting the tank from scratch just finishing up college and hope to get up and running in a month , trying to get the substrates etc I want is a hassle with shipping, also I might try the halide oh this tank gives fierce plant growth. So a month is my aim.

Good Man Derek , Are you catching the Planted tank bug?

Cheers
Alan

Interesting experiment I always liked Toms work as he goes into smallest details. He does not assume that something happens, he proves it.
As for experiment itself it's not new to me as from my small experiments in uncontrolled environment I've found that CO2 takes long time to difuse.
In my tanks I start CO2 5-6 hours before the lights. I've noticed that in big tank it takes much longer to reach optimum CO2 levels compared to small ones.

Does the temp also have an effect on CO2 solubility into water? Higher the temp the less CO2 is disolved into the water? Also can a higher PH allow more to disolve?



Mark