A Different method to measure CO2 flow rates, like PAR vs Watt/gallon - The Planted Tank Forum
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post #1 of 5 (permalink) Old 01-31-2013, 10:20 PM Thread Starter
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A Different method to measure CO2 flow rates, like PAR vs Watt/gallon

Frankly, I've never used bubble rates too much, just a rough gauge, an estimation. Then I spend a fair amount of time dialing in the correct rate for that tank. I do not like having to do that process again and again, anytime I switch out CO2 equipment.
I loath that chore.

Someone, a client, asked me how to adjust high rates a few years back. I said using a few different bubble counters etc.
He came back with a 1200$ programmable mass gas flow controller. Okay that works nice, but it's 1200$.

Just to measure CO2.

I found a big leak in my solenoid(clippard), so I needed to remove it, and I'd just gotten a couple of nice dual stage CO2 reg builds from Oldpunk.
So the problem is how to set the bubble rates exactly like the old set up regulator?? Yes, I could have just removed the solenoids, but I have these nice pretty Dual regs, and well, wanted to switch them out anyway. 10-20 years is enough service for the old Victor single stages. Maybe I'll sell them, err, without the leaky solenoid!

The solution is deceptively simple and it works quite well.

I used a 2 liter flask and inverted it in the aquarium, then took the CO2 line from the old reg, and got a feel for the general bubble flow rate, then dialed the new Dual stage reg to about the same bubble rate.
I used the stop watch on my iPhone to measure time, then measured the old reg vs the new reg's fill rate to 500mls(this took about 4 minutes). My 1st attempt was lucky, I got to within 30mls, I adjusted the CO2 up a tad(1 click/notch) and I put the new regulator back on.

So the old reg: 500mls in 239 seconds
The New reg: 500mls in 249 seconds

Not bad, and a better method that bubbles per second which is impractical for larger tanks. This method addresses variations in bubble sizes and tubing size differences also, so it's a much better simple method to measure the RATE of CO2.
Once you get it close, then you can tweak a little each few days and observe.

You do not need to use some $$ glassware, a large container will do where you can view the gas inside, and then make a mark at say the 2-5 min point. Then try and match that flow rate with the new regulator.
You can also estimate based on the time you have the CO2 gas "on" and how much CO2 gas volume is in the tank, pretty close how long the gas tank will last, before running out.

ml/min of CO2 is a better unit than bubbles per second, much like PAR vs Watts/gallon.
This is a better comparative measure for CO2. Yes, you can use the pH/KH "relative" measure also, and likely should use that in conjunction.

My old pH dropped to 5.9 or thereabouts. I'll measure it tomorrow and see how close that matches up.
Then do another KH test also(colorimeter).

All this checking needed?
Well, lots of fish and nice well run tank, I want the same CO2 rate when I do the switch, this will also give me a good idea how much the rate is for a similar tank set up.
Much better than bubbles per second.

Note, you can do this for smaller tanks also, but you will just not get as much flow etc.
You can also extend the time and volume farther out for greater accuracy.

So say you have a nice CO2 set up for a mini L, you can do this method if you switch CO2 systems using say 15 minutes and say 50mls of CO2 gas.

Tom Barr
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post #2 of 5 (permalink) Old 02-01-2013, 12:53 AM
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You can also do this with plastic bags/garbage bags. We do a similar method at work where we hook up garbage bags to a vacuum exhaust to measure the rate when we switch out pumps. Most ziplock bags have the volume on the box.
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post #3 of 5 (permalink) Old 02-01-2013, 05:49 AM Thread Starter
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If you do not have some stable comparative method for light and CO2, you really don't know Jack.

Unlike Drop checkers, pH/KH, bubble counters, you really have no good comparative method for the rate of gas being delivered to the aquarium volume.

It's like the PAR vs the watt/gallon issue.
This method allows aquarist to compare the rates, and get a pretty good idea how much gas is required to run the tank nicely.

If your tank is doing really well, then do this, write that volume per minutes(5 or so minutes should be good, you can go longer for smaller tanks, like a 5 Gal etc/nanos etc).

Any container you can see the bubble form... will do. Once you know what a good well run CO2 rate is for that tank, then you can check if something goes sour.

Obviously if your tank does real well and the plant biomass doubles over time, you will need more CO2, so another measure will be done in such cases.
This happens between trims with my 120 Gallon. I use about 20% more when it's filled, vs post harsh trim. This method can easily standardize the CO2 and is dirt cheap to do, well, pretty much FREE. And it's very useful if you have issues with CO2, which means everyone.

Tom Barr
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post #4 of 5 (permalink) Old 02-26-2013, 12:31 PM
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When you capture the gas into the flask, is it out of a diffuser unit or bare tube.
ie: Does a diffuser unit affect flow to any significant level.

Have you done any sealed tank tests to determine ratio out-gassed CO2 at the surface to input to get an estimate on saturation and plant up-takes?
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post #5 of 5 (permalink) Old 05-27-2013, 06:14 AM
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Interesting post and happy 12,000 Tom.

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