CO2 meter on low tech?

CO2 meters cost a fair bit, but a drop checker doesn't have to. I'm betting a low KH solution might reveal a bit about a tank. Try reducing surface disturbance for a few days, then run an airstone after. You could keep the variables in decent check doing one after the next in the same tank.

I've got my own conclusions based on indirect calculations of respiration and approximating degassing rates, but a more direct test would be far more telling.

-Philosophos

 

Just take some of your 4kh solution and use it in perhaps a 1:7 or 1:3 solution with DI H2O. 1:7 would be .5kH, 1:3 would be 1KH.

Depending on how things go I might be able to run the experiment at the same time as you. I'll know by tomorrow.

I doubt this will be anything conclusive in terms of fine details, especially given the difficulty of controls. Still, if it's highly reproducible and yields definite results, then it'll be a great way to settle the issue. Tons of people have drop checkers and 4KH solution that they can dilute.

-Philosophos

 

I'll be starting this little experiment tommorow for the air pump test. I wouldn't mind if everyone gave a read over and added any aother variables they think would be relevant to the test. Unfortunately an accurate pH test of the column is out of the question right now as the electrode in my meter drifts horribly.

The tank is a standard 10 gal with one pair of ~4 inch long albino bristlenose and a plant density that should be decent enough to represent the average tank. Filtration will be a Whisper 10 power filter (90gph) without media, and a Stellar 20 air pump running 2.2gph at 2.9psi.

The drop checker is a generic one from Aquatic Magic. I will be adding aproximately 2-3ml of .5 KH (8.93ppm) solution to it achieved using sodium bicarbonate, along side about 2 drops of low range pH indicator containing bromothymol blue. the drop checker will be placed in the front left corner, farthest away from the airstone in the back left. I hope to make observatons every hour or two.

As for the test without the air pump, I'm a little more unsure ofhow to do this. I can't spend an entire week at home taking hourly measurements. I could take measurements at the same time of day towards the end of the light cycle.

I understand that a drop checker isn't going to give me the most accurate reading in the world, but I do hope that the saturation difference will be by enough to offer a very distinct difference in color. Hopefully one that will be noticable if I take pictures.

-Philosophos

 

The only variables I can think of would be temperature ( presumably controlled ) since that would affect all sorts of metabolisms. You would also need to make sure you don't have any sort of surface film which would affect your gas exchange ( also presumably non existant ).

-
S

 

Temperature would be a good one.

How do the "don't disturb the surface" type react to surface film? I'd almost think it desirable.

-Philosophos

 

I have no idea. I know that if there's a film and my discus are breathing a little hard removing the film alleviates that. Whether that's a gas exchange issue or maybe a getting rid of crud in the water that's decomposing and letting the filter "catch up" I don't know. I'm inclined to go with gas exchange not letting in the O2. I'm not sure how I'd test and I'm more inclined to just clear the film off and not worry about it, but I can see how it might be a heavy influence.

-
S

 

Here's a link to a thread on the subject of measuring CO2, from APC and Diane Walstad.

http://www.aquaticplantcentral.com/forumapc/el-natural/66175-co2-levels-my-npts.html

What do you think?

Bill

 

I'll just let the tank play out as it will then. This is an experiment I hope to seen prove through repetition with others rather than finite variable control.

I would've started the first phase, but things came up today; posts, plumbing issues, vomiting. I Will start tommorow if I have time/feel better.

-Philosophos

 

I'm not quite sure how I managed to make a post that short in reply to everything that's been said. I must've missed a couple of posts.

The IR method is neat, Tom. I think I saw you post on it back when you and Vaughn were working on the CO2 meter with osmosis membrane and KH solution. Looks like it'd cost a small fortune to operate though; chromatography membranes aren't cheap.

Anyhow, I'm hoping to get answers in this case that will not work on precisely calibrated numbers. The color of one drop checker with the same indicator solution, in the same tank will show if there is a significant difference within this tank between having the air stone there and not. The concept here is not about getting precise numbers; I simply don't have the means to do that right now. If someone donates some equipment to me then we'll talk

What I do have is the means to show that under almost the exact same circumstances with the presence/omission of an air stone, more/less CO2 was present. I want others to be able to do the same who ask themselves the question of whether or to use surface disturbance or not. It's a simple experiment that can be done for less than $20 of materials, and most of us have those materials sitting around.

Right now my drop checker with air stone in is actually not sitting far off reality; about 2.33-3.76ppm CO2 would be the actual number it correlates with. It's been holding steady during the hours that the light is on since yesterday.

If there's no noticable differene when I turn the air stone off and let things sit with a HOB for a few days, then I'll call it a day. If I get a nice blue or bright yellow drop checker, then I've come closer to answering a question within the hobby. Maybe someone else will build on it, or I'll eventually have the resources to do a better test.

-Philosophos

 

The posts didn't take that long. Most of it had to do with the puking actually

Might explain some of my hairbrained/half-assed post as well.

I've never known science to work any other way. If the theory is sound, there should be multiple ways to test the concept. Unfortunately this hobby is light on the science end quite frequently; most of us don't seem to know why what we do works on some of the most essential levels.

So the system compensates for its self in a way by taking up more CO2 as it's offered. At the same time (from what I've read) plants manufacture less rubisco in higher CO2 conditions. This would mean plants take up far more of the CO2 preportionately in low CO2 environments?

-Philosophos

 

Sounds like you'd have to obliterate an entire tanks contents; dry it, crush it send it through flash chromatography, etc. Definitely more difficult and costly than anything anyone cares to invest into this hobby right now. Perhaps large companies would, but I don’t imagine they’d give us the benefit of that information. They’d just charge us for it in their products.

Still, it’s good to know how you’d go about it. I’m always curious as to the methods people like you use to figure out how tanks work.

As an update to my little experiment, things were running around the 6.6-6.8 mark in the drop checker. I’d estimate somewhere around 2.8-3.4ppm CO2 based on the color. Unfortunately Mrs. Philosophos decided to re-introduce a fish from the quarantine, add another, and use tank water to adapt. Results for today are scrapped.

I’m not sure when I’m going to get an entire day to monitor things again. I’ll probably just create a new thread for the whole works once I’ve got my results.