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Beasts 02-06-2019 12:53 PM

I Must Be Doing Something Right
I just read on that a 40 gallon aquarium, in their estimation, would use about 5 pounds of CO2 every 3 to 4 months. I just purchased a third 20 pound cylinder for my 410 gallon aquarium and the first 2 cylinders lasted an average of 4.6 months each! I realize that a lot of parameters go into CO2 usage but, according to the above estimate, it should take somewhere around 60 pounds for 4.6 months in my aquarium considering just the volume.
I have paid a lot of attention to flow rates and flow patterns of the water in my aquarium and done a lot to avoid off gassing. The outlets from the filter are below the surface and directed toward different depths. With outlets at each end of the tank I establish a circular flow pattern which I switch from clockwise to counterclockwise and then back once a week. This distributes the CO2 throughout the aquarium and also helps avoid detritus buildup. There is essentially no disturbance of the surface water in the aquarium but all of the water for my wet/dry is drawn from near the upper surface. The tops of the prefilters and the wet side of the wet/dry are not sealed but are covered pretty well. My CO2 reactor is very efficient in that I never even see the CO2 entering the aquarium it is so well dissolved. I got the impression that misting might be better but I don't understand why. My plants are pearling like crazy and multiplying and growing rapidly. On a scale of 1 to 4 they are mostly ones and twos so that is undoubtedly aiding my success but the aquarium's being 30 inches deep adds to the challenge.
My injection system also maintains the pH between 6.7 and 6.9 by automatically turning the pH flow on and off. So the CO2 level is consistently at a good level without waste or over dosing. My understanding is that, considering my water hardness, this pH level maintains a good CO2 concentration. The system I use is definitely pricey but considering the convenience and consistency of the function I consider it money well spent especially with a tank of this size. Part of the convenience is due to the fact that it does not use a bubble counter which necessitates a lot of readjusting but is, instead, electronic.
Forgive me if a lot of this sounded like bragging. I didn't intend to do that. I am pleased with what I have but it is also the result of a lot of research, hard work and experimentation. I am hopeful that some of you find that what I have to say is of some value to your applications.

mistergreen 02-06-2019 02:06 PM

Re: I Must Be Doing Something Right
So you're using your pH meter to control a CO2 solenoid? Keep it calibrated often.
I've been playing with an actual CO2 sensor for a while but haven't had the time lately.

Beasts 02-07-2019 10:22 AM

Re: I Must Be Doing Something Right
My pH meter is not part of the CO2 injection system. There is a pH probe attached to a pH controller. The probe is mounted in the filter line that leads to the CO2 reactor and samples the pH constantly. The controller then turns the CO2 on and off.
The pH meter is used to check the controller for accuracy and to measure the pH in my other aquariums, the RO water, tap water - before and after the softener, and water from our source, the pond in the back yard. I got tired of getting water samples, mixing with the reagent and trying to match a color chart, a process which is only accurate to within .2 points, if you guess the right shade of green. The meter is much quicker and more accurate.
You can find the system I have on where it is called CarbonDoser. Where have you found a CO2 sensor and can it be programmed to maintain within a certain range? I would love to check out how they function.

mistergreen 02-07-2019 01:38 PM

Re: I Must Be Doing Something Right
Is there a way to calibrate the carbonDoser? I see an issue with that if you can't. All sensors drift in value. You could be dialed to 30ppm but you might get +- 10ppm. That's a problem.

I use this CO2 sensor.
It's self calibrating to the lowest value, which is atmospheric CO2. So when you want to calibrate it, you take it outside or blow atmospheric air into it.
You'd have to program your own micro controller like an Arduino or ESP. Getting it wet is a major problem :)

I'm tempted to start a crowdfund to finish this project, if people are interested. I remember a project on Kickstarter that die..

Beasts 02-08-2019 09:51 AM

Re: I Must Be Doing Something Right
The CarbonDoser is not calibrated to the CO2 concentration directly. The pH controller simply turns the CO2 flow on and off based on the pH. Once the CarbonDoser is turned on by the controller the CO2 is released at a very consistent rate. The rate of flow of CO2 is determined by the CarbonDoser via the bubble rate (electronically) and the size of the bubbles (by the pressure). The pH probe attached to the pH controller can be calibrated using buffers.
The CO2 concentration is determined by the relationship between the pH and the hardness, the way I understand it.

hoppycalif 02-08-2019 12:01 PM

Re: I Must Be Doing Something Right
It can be accurate to rely on the change in pH to determine the change in ppm of CO2, but it isn't accurate to use the combination of KH and pH to determine actual ppm of CO2, unless the water involved has nothing dissolved in it that affects pH except CO2 and carbonate ions. Aquarium water doesn't qualify.

Beasts 02-09-2019 10:38 AM

Re: I Must Be Doing Something Right
Okay, good to know. However, is there a meter that measures CO2 concentration in water? If not, what factors can I use to increase the accuracy of my pH controlled CO2 injection system in order to find the actual "sweet spot"? As mentioned above my plants are growing, pearling, spreading and flowering quite nicely but are those the best indicators we have to go by?

mistergreen 02-09-2019 12:06 PM

Re: I Must Be Doing Something Right

Originally Posted by Beasts (Post 995279)
is there a meter that measures CO2 concentration in water?

CO2 sensors. You can measure CO2 right above the water to determine the CO2 in the water or you can water proof the Sensor and use a CO2 permeable membrane and submerge it in the water. The underwater CO2 sensors are used by scientists and cost thousands of dollars.

You can use a drop checker with a controlled kh solution to give you a decent estimate of CO2. The ph , kh, co2 relationship does work in a controlled environment like a drop checker.

As long as your plants are growing and pearling, go with it, as long as the fish don't die from OD.

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