# CO2 Flow Meter, What's Your Setting in CC/Min/Gallon?



## sdwindansea (Oct 28, 2016)

Doesn't it also depend upon the regulator PSI and type of reactor used (along with other factors)?


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## Ken Keating1 (Nov 22, 2017)

There lots of variables, but I'm just trying to ball park it. Even with pressures, the gauges have such large scales the reading could easily be off, not to mention the quality or accuracy. 

My output pressure is set at 40 psi, and I'm using a GLA inline diffuser with a reactor afterwards.


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## PlantedRich (Jul 21, 2010)

On a 20 gallon, I try to run .3 SCFH and about the same on a 75. They both run off the same reg but different from there on. Different needle valves feeding two Grigg's reactors but once it hits the tank, the results are totally different. The 20 has lots more circulation than the 75 and the plants and fish are totally different.
I will let you do any calculations on how that amount compares to your readings?? >


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## Ken Keating1 (Nov 22, 2017)

@PlantedRich: Not only do I get to convert from SCFH to CC/min, you're also making things more interesting by using the same flow for two very different sized tanks-there goes my ballpark estimate!!!

For your tanks the flow rate is 142 CC/Min. For the twenty, this converts to 7.1 cc/min/gal and the 75 at 2.0 CC/Min/Gal. Do you know what the output pressure is at your regulator? I would assume it's fairly low. What's the scale range of your flow meter? If your flow is close to the low end, it could be off.


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## PlantedRich (Jul 21, 2010)

Yes, fully agree that flowmeter are prone to being off. I find they totally stick if I let water get into the tube where the little black ball floats! 
The reg output is close to ten PSI, just enough to push CO2 into the reactors against the minor pressure from the tank water column height. The model I use has a range from 0 to 1.0 SCFH, so I am running nearer the low end than center much of the time. I've tried running one flow a bit higher at about .5 but found no real reason to keep one tank higher, so I had backed that tank down a little as the fish were showing breeding action. That was a bogus attempt, though as they are rainbow cichlids and I was not sure of the M/F part of the pairing. After seeing them get the "warpaint " coloring and disappear into the brush for a few days, I am now pretty sure they were both female. I suspect one was laying eggs but nobody fertilized them, so no fry appeared!
The first pic is the 75 with lots of big wooly stuff and the second is the twenty with totally different planting and fish.
I'm not finding a good way to say what each tank may seem to need without actually letting the plants and fish decide. 
I do like the flowmeters for giving me real numbers to set and adjust but that is more useful after the fact than as I set up.


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## Jack Shaftoe (Apr 29, 2006)

What's your lighting situation and your plant selection?

Honestly, a flow meter is unnecessary.

With all of those swords you shouldn't be having a problem. I suspect that your lighting needs a tweak.

Ok. 400 gallons. Zero flow meter. It took me months of observation to realize how this system needed to work. Then it became 'easy'. Plus weekly 50% water changes and subsequent dosing. Perhaps be more patient? Add more stem plants or fast growing floating plants to filter. Find relative equilibrium.


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## burr740 (Feb 19, 2014)

75 gal #1 runs about 30 cc/min. It has one canister filter with a built in skimmer

75 gal #2 runs about 38 cc/min. It has two canisters with built in skimmers. 

Otherwise same filters, reactors and working pressure. Those little SunSun skimmers dont look like much but they make a big difference. If I ever forget to turn them back on after say a big trim, fish will be gasping at the surface a few hours later and the PH will be a couple tenths lower than its supposed to be. But I digress...

My previous 120 gal ran about 60 cc/min

Also have the Dwyer models, two 5-50 and one 10-100. These things are great!


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## SingAlongWithTsing (Jun 11, 2015)

Throwing my numbers for comparison.
according to my flow meter im at 80ish cc/min. 134 Gall w/ 55 gallon sump, I have a power head on it if it matters. about 20 PSI working pressure. modified cerges reactor.

if i run a co2 line straight from my flow meter to the sump im at 95~100 cc/min, inverted cup method matches this number.


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## Jack Shaftoe (Apr 29, 2006)

Overkill. Measurements like that are unnecessary in a system that has reached equilibrium. 
Strive for observational equilibrium. It's much easier.


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## Greggz (May 19, 2008)

45 cc/min in my 120G.

Heavily planted, high light, high surface agitation, cerges reactor, 20psi, 1.35 peak CO2 drop.

I really love having the flow meter. Should be standard on any larger tank (55+ gallons). Makes tuning and maintaining your CO2 flow so much easier. Highly recommended.


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## Grobbins48 (Oct 16, 2017)

Setting one up on my 29 gallon right now, and the one for my 55 will be here Monday. Both the RMA-151 SSV. Excited to use them. It seems to me that the flow is all relative based on pressure, diffusion method, filter method, flow, surface agitation, etc. But the benefit woul be, especially for the bigger tanks, to be able to dial in better with a relative scale you can see vs. bubble counter that is hard to measure. It really is your measurements relative to you that matter!

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## PlantedRich (Jul 21, 2010)

The value of any piece of equipment can always be open to debate. A fellow from Southern California recently questioned the need of heaters until we discussed that he might be spoiled!! 
Using a flowmeter is one of those which can be overkill for some but really worthwhile for others. I see them as replacing a bubble counter. Anybody who runs very much CO2 is going to see a bubble counter as almost useless as the "bubbles" are just more solid stream than bubbles that one can count. Not necessary to know the bubble count but many of us do want to back the pressure off to avoid damage to the reg on restart like after we change a CO2 tank. We can set a timer and do our best to count bubbles which we can hardly see and call it good enough or we can use a flowmeter. When I change out a tank, I do try to reset the working pressure to the same as before but that is depending on the gauge and the error of parallax to all be "good enough" to get me the same flow. When I use a flowmeter, it is not a quarantee that I return the settings to the same point as all things mechanical do have a certain amount of error. But given the choice between a guess at how many bubbles are passing and having an actual number on the flowmeter, I am going with the flowmeter as far more accurate! 
I could do away with using a thermometer in the tanks and just feel the water but I like to get that reading closer, just as I want to get the CO2 flow closer.


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## vanish (Apr 21, 2014)

Running ~20 cc/min on my 75g. Sunsun 304b and a ~350gph powerhead, Griggs reactor.

I think I could go higher, but I am not pushing a ton of PAR, so see no need.


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## Záyne (Feb 12, 2018)

Do you guys run the CO2 straight from the regulator (solenoid) to the flowmeter, or do you run it through a metering valve/needle valve first? If yes, what benefit does that have?


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## jeffkrol (Jun 5, 2013)

Záyne said:


> Do you guys run the CO2 straight from the regulator (solenoid) to the flowmeter, or do you run it through a metering valve/needle valve first? If yes, what benefit does that have?


Flow meter has a metering valve.. Well you can get it w/ and w/out one..
The ones most mentioned have the metering valve..


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## Grobbins48 (Oct 16, 2017)

Záyne said:


> Do you guys run the CO2 straight from the regulator (solenoid) to the flowmeter, or do you run it through a metering valve/needle valve first? If yes, what benefit does that have?


All depends on the equipment. There are flowmeters, like the Dwyer RMA-151 SSV, that have integrated valves (SSV stands for stainless steel valve, they also have a brass one) or you can get just a flow meter with no integrated valve (Dwyer makes these also, like the RMA-151 or 150). If you use the one with a valve then there is no need for a needle valve before the flowmeter. If your flowmeter does not have a valve then you will need to have a needle valve before the meter to regulate the flow. 

The idea of a flowmeter is that it replaces a bubble counter and can make it easier to make adjustment and keep consistency on large tanks where a bubble counter would otherwise look like a constant, uncountable, stream of bubbles. We all still need some sort of valve to regulate the amount of flow, whether integrated or not depends on each person choice I equipment.

I personally run the RMA-151 SSV on my 29 gallon (still new to me) and will also be setting one up on my 55. The actual flow is not necessarily relevant due to so many variable, including but not limited to diffusion method. The 29 gallon uses a ceramic diffuser, while for the 55 I'll be building an inline reactor. Do what works for you!!

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## jeffkrol (Jun 5, 2013)

Grobbins48 said:


> I personally run the RMA-151 SSV on my 29 gallon (still new to me) and will also be setting one up on my 55. The actual flow is not necessarily relevant due to so many variable, including but not limited to diffusion method. The 29 gallon uses a ceramic diffuser, while for the 55 I'll be building an inline reactor. Do what works for you!!
> 
> Sent from my SM-G950U1 using Tapatalk


Well we both hit that one but got a physics problem but need some real world "evidence".
First I know purely a guess no matter which way but the idea of a conversion factor for those switching back and forth is somewhat helpful..

First the math Converting bps to cc/min:


> 1/8" is 3.175mm = .3175cm diameter bubble. = .1588 radius Volume = .01677cc x 60 = 1
> 1 bubble sec = 1cc per minute
> 
> Of course bubble size matters.
> ...


I know each bubble counter probably puts out diff size bubbles and due to the cubed function that allows a large variability to creep in..

By any chance do you have a bubble counter to put in line to your flow meter to get an idea of which number would be the best fit? 
Or none of the above numbers..

Point is if someone was switching from bps to cc/min (sticking w/ metric for now) then they would know the correct range to buy..


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## Grobbins48 (Oct 16, 2017)

jeffkrol said:


> Well we both hit that one but got a physics problem but need some real world "evidence".
> First I know purely a guess no matter which way but the idea of a conversion factor for those switching back and forth is somewhat helpful..
> 
> First the math Converting bps to cc/min:
> ...


Yeah it's a good point. I just these past few days got the flowmeter running so no good comparisons yet. Still dialing In what working pressure I want and how much flow from the valve. I suspect at least a week or so before I really have a better feeling how it works on the smaller tank. Probably don't need it on that one, but more of a learning learning experience the. Will use one on my 55 which is not yet planted. 

I'll see if the bubble counter I have can work with the tubing I am using. Will check this weekend, and try and get some numbers.

Every day learning something more about the hobby!



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## burr740 (Feb 19, 2014)

There are only two options using Dwyer cc/min models, a 5-50 and a 10-100. The 5-50 is gonna work for most tanks.

Most 40Bs or 55 gal are going to be in the 20's. If you have a smaller tank than that you probably dont need a flow meter in the first place, because chances are you can easily count bubbles.

My 120 gal used about 60. That's pushing a good bit of co2 relative to most folks (higher ppm), and two skimmers which make for a lot of off-gassing. Greggz 120 only uses 40-something

So to be on the safe side 100 gal + tanks might wanna go with the 10-100, anything smaller the 5-50 should work fine.

Posted this in the GLA thread but its more relevant here. If it seems rambling at times I was replying to a jeffkrol post -

Id say if you're able to count your bubbles then you really dont need a flow meter. By count, I mean look at the bubble counter and say yeah that's about right.

They are most useful when you're running too many bubbles to count, more or less a steady stream that could be off several bps and you couldnt tell by looking. Only way to know is check the PH

As for this -

"one bubble per second is about .85 cc per minute'

Wouldnt that depend on the working pressure? Or more specifically the resistance at the diffuser, reactor, etc?

CO2 bubbling through an open line makes really big bubbles. Pushing through a diffuser that needs 35 psi the bubbles are really small. Maybe its the same amount of co2 just more compressed? Idk...

Which brings us to the accuracy of these flow meters. By accuracy I mean is 30 cc/min really 30 cc/min, or is it more or less? Most flow meters have an accuracy rating. These Dwyers I believe are +/- 8% depending on the model.

The thing is it doesnt matter because the number is just a personal reference point. If you know 30 cc/min according to the scale is the sweet spot for your tank, it makes no difference if that's actually 25 or 35, you know 30 is where to set the thing.

Another thing about converting bps to cc/min, assuming you want to do this for the purpose of knowing where to start, it's a whole lot easier to keep the bubble counter in the beginning. That way you can start out running about the same as you were before and see where the number falls on the scale.

Set the working pressure to whatever, open the regulator's metering valve wide open, then use the flow meter to hit the approximate bubble rate that you're used to. Then you can ditch the bubble counter later on if you want to, or just let it run dry.

Personally I still have all mine running. I use inline types that are a good ways after the regulator, some are suction cupped inside the tank. I really dont need them now just been too lazy to take them out. And I do like being able to see exactly what the system is doing, a triple check if you will.

The point is with a flow meter you have a number to go by instead of trying to eyeball things according to what a stream of bubbles looks like. Again, it's mainly for big tanks.

If you can count your bubbles then you already have a reliable reference point. A flow meter probably isnt worth the trouble.


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## Ken Keating1 (Nov 22, 2017)

I use a metering valve and I adjust flow either one of two ways:

(1) I open the flow meter valve to full open, then set the needle valve such that the flow is a little higher than what I need, and then adjust/fine tune via the flow meter, or 

(2) Open the flow meter valve fully open, then adjust to the metering valve. The metering valve has a turn counter, so it's very easy to make fine adjustments.


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## PlantedRich (Jul 21, 2010)

While the flowmeter does have a valve to adjust flow, it may not be one which can be tuned to the fine point we like. 
What makes a good needle valve is lacking in the flowmeter valve. Two big points to getting just the right tiny amount of change we often want is the taper on the needle being long and sharp and the threads which move the needle need to be fine also. Looking at a bolt or screw, we can see the difference in a bolt with 20 threads per inch versus one with 32 threads per inch. Turning a Number ten screw with 32 threads per inch will move it far less than one with 20. So the flowmeter with a short valve, can't have a long tapered needle and it also is not likely to have the fine threads to move the needle forward/backward just a tiny bit. 
A bit like sticking a finger in a hole versus a fine pointed stick. Just less easy to get just the right amount. The big problem for our use is that we are using really small amounts and we are really fussy about that amount.

Bump: If one has a CO2 setup running and wants to know how much CO2 he uses for the purchase of flowmeters, I like measuring if it is easy. And it can be easy! 
Most of us have a calibrated bottle or tube like a test tube handy. So to see how much your current bubble count is, take the tubing off the diffuser or whatever you use and stick it up into an overturned test tube, etc. If you get "X" number of bubbles per minute and get "Y" ml per minute in the tube, you have your number without too much thought. 
You will have to adjust the numbers and whether you measure in ML, teaspoons, or whatever volume your test tube is calibrated with.


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## burr740 (Feb 19, 2014)

PlantedRich said:


> While the flowmeter does have a valve to adjust flow, it may not be one which can be tuned to the fine point we like.
> What makes a good needle valve is lacking in the flowmeter valve. Two big points to getting just the right tiny amount of change we often want is the taper on the needle being long and sharp and the threads which move the needle need to be fine also. Looking at a bolt or screw, we can see the difference in a bolt with 20 threads per inch versus one with 32 threads per inch. Turning a Number ten screw with 32 threads per inch will move it far less than one with 20. So the flowmeter with a short valve, can't have a long tapered needle and it also is not likely to have the fine threads to move the needle forward/backward just a tiny bit.
> A bit like sticking a finger in a hole versus a fine pointed stick. Just less easy to get just the right amount. The big problem for our use is that we are using really small amounts and we are really fussy about that amount.


Right. Which is another reason flow meters are only good for bigger tanks.

Lets say you have a 20 gal and want to go from 2 bps to 2.5, or less. Cant do that with a flow meter.

But on a big tank that extra .5 isnt going to make a dent one way or the other, so its not the kind of adjustment you'd make in the first place.

Most definitely if you want the ability to make small precise adjustments stay away from flow meters. Get a quality metering valve instead.


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## PlantedRich (Jul 21, 2010)

burr740 said:


> Right. Which is another reason flow meters are only good for bigger tanks.
> 
> Lets say you have a 20 gal and want to go from 2 bps to 2.5, or less. Cant do that with a flow meter.
> 
> ...


Or one can use a flowmeter to see what's happening and use a good quality needle valve to do the adjustment. If one wanted to get really super obsessed with knowing, one could also keep using a bubble counter as well as the flowmeter. I don't find one to not allow the use of the other. It all falls into what I call tools. 
Like buying a car, we certainly can do without lots of the things we pay extra for on a car. One can always use a paper map but I really, really, like using a GPS but I do have both GPS and a paper map in my cars! :surprise:


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## Ken Keating1 (Nov 22, 2017)

Bubble counters and flow meters are not truly letting us know how much CO2 is flowing, they’re just giving us a value (bps or cc/min) to use as a baseline from which to make adjustments from. Flow meters are accurate to +/- 8%, but that’s at a pressure of 14.8 psi at 70 degrees. Any difference in these parameters you can use formulas to calculate how much CC/Min you’re using, but the issue being is the accuracy of our pressure and temperature gauges, how clean the flow bead that’s inside the flow meters., and lots of other parameters. For bubble counters, the big issue is pressure; depending on the pressure, how much CO2 is in that bubble can vary greatly, plus counting, is that 1.2 bps or 1.4 bps?

The only way I believe we can truly determine how much CO2 we’re using is by either:

1. Using flow meter at the values it’s been calibrated for, and the majority are calibrated at14.8 psi at 70 degrees) or,

2. Using mass flow meter and these are can be quite expensive, or

3. Weigh the tank and then weight again say a month later and the difference in weight would be the weight of CO2 we used. If you have your solenoid on a timer, you would know how many hours CO2 was flowing, and from there you could do calcs to determine how many CC/Min of CO2 at 14.8 psi and 70 degree you were using. It would be interesting to see how close this value would be with the value on the flow meter.

But since there are so many other issues (tank size, plant load, reactor type, etc) that come into play, going to this level of effort is not really required, because the bottom line is how are fish and plants are reacting to our flow, that’s really what we adjust to, we don’t adjust to particular value.

I agree with all who listed the advantages of flow meters. One advantage not mentioned is that while on vacation, it allows the pet sitter, who in my case, knows nothing about aquariums, to be given a value to check against, and if something is not correct, can give me a call to trouble shoot. Having a value that one can read does make it much easier to know the system is operating correctly.


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## PlantedRich (Jul 21, 2010)

Rather than going for great accuracy in knowing how much is used, I see the flowmeter as more of and advantage in ease of use. I can walk by and see the little black ball is in the normal place and take less than a second to say it is "right". If using a bubble counter alone, I can't count the bubbles and if I could, it would require much more time and effort to count and time. Either can work better for different uses and reasons. 
Look, learn, and adapt as needed!


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## gus6464 (Dec 19, 2011)

I'm just waiting for the Seneye Planted to launch. Co2 reading right away without waiting 3 hours on a drop checker.


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## Grobbins48 (Oct 16, 2017)

On my 55 with a DIY cerges style reactor, I can get drop checker to lime green with 12ish cc/min at 40psi. Running the reactor is a Sunsun 304B with pre-filter 602, 4L of bio media, 2 purigen packs, and 300g charcoal. The intake also uses the surface skimmer. I have no bubbles coming out of the spray bar.

My 29 is actually running more cc/min with a HOB filter and ceramic diffuser to get the same results (~15 now).

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## GoldenCelia (Apr 28, 2018)

Hi, I'm new to the forum and this topic drew me in. I bought a Dwyer and really like it. Thanks to you all. I do have a question about using it.

I have needle valve and it seems to me that the valve on Dwyer is useless as far as controlling the flow. I find that the needle valve is better. I had hoped that I could dial in the region I want in flow with the needle valve and then use the Dwyer to fine tune it. As an example I would dial in maybe 10cc with the needle valve and then move it a couple of cc's with the Dwyer valve but it doesn't seem to be at all sensitive. Is this what you find?


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## Grobbins48 (Oct 16, 2017)

Yeah the dwyer valve is not the best by far, takes patients and time to get it where you want, but once you have it set you are golden. The reason I like it is it wont move once set, and I have numbers vs bubble count to go by for injecting the CO2.

If you have a needle valve that is better than the one on the flowmeter you could always use that online before the flow meeter and keep the dwyer one wide open. Using two valves really wont give you any benefit, so just use the one that works better for you! 

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## Ken Keating1 (Nov 22, 2017)

Yes, there is very little fine tuning with the flow meter valve. If you want to try, the easiest is to set the upstream needle valve at a flow that just a little above the flow rate you want, and then use the flow meter valve to reduce the flow.


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## FreshPuff (Oct 31, 2011)

*Dwyer RMA-151-SSV*

is what I use. I have a 50 gallon sumped aquarium with an inline Griggs reactor and lots of surface agitation. I am at roughly 30cc/min and on my old Ista bubble counter that was about 5 bps. 

My flow meter's ball tends to jump around within 5cc.... The ball fluctuates between the 30cc-25cc marks on the gauge. Those of you with a Dwyer flow meter, does yours do this also?


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## Greggz (May 19, 2008)

FreshPuff said:


> My flow meter's ball tends to jump around within 5cc.... The ball fluctuates between the 30cc-25cc marks on the gauge. Those of you with a Dwyer flow meter, does yours do this also?


It shouldn't.

Are you using the needle valve or the flow meter valve to adjust? I have the needle valve pretty wide open and use the meter's valve.

Here's a quick video of me adjusting mine. Once it's set, it doesn't move.


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## Ken Keating1 (Nov 22, 2017)

Greggz valve operation is smooth, I'm envious. With mine, I can put a little force on it or tap it and it jumps around. I typically use the needle valve at the reg to adjust mine.


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## burr740 (Feb 19, 2014)

One of mine jumps around whenever you adjust it, also when it first comes on, then it settles down and stops somewhere after maybe 5 minutes. So like if it's sitting on 30 and I want to go to 35, I have to move the knob a little then wait and see where the bubble finally lands, repeat if necessary. 

My other one works very smooth like Gregg's

Both are rock solid as far as consistency from one day to the next though.

I run the regulator's needle valves wide open and use the flow meter to control the flow. Crappy needle valves are the main reason Im using flow meters. Fine tuning precision is not that important, I just want it running the same every day.


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## OreoP (Aug 12, 2016)

Both of mine work smoothly like Gregg's. Have the needle valve wide open and regulator set at 25psi. Only time I need to adjust is when I replace the tanks


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## Williak (Jun 26, 2012)

This is a great thread to discuss. Planning to purchase a flow meter today for my aquarium (80g). Tired of having same issues as listed by everyone else here

Thank you to everyone who clarified about leaving needle valve wide open then adjusting with flow meter. I was very confused trying to think about how I’d get an accurate (relative) reading on the flow meter if the needle valve was also controlling release of co2 prior...

Can’t wait to test it out and will update with my numbers when I get it dialed in!

-


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## Grobbins48 (Oct 16, 2017)

Both of mine are smooth, one used and one new old stock. 

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## FreshPuff (Oct 31, 2011)

Hmmm looks like something is not right with my setup then. Maybe its the regulator or the flow meter. Ill start a new thread with additional questions so I don't hijack this one. Thanks for the responses.

FYI theres an individual on evilBay who's selling the dywer rma-151-ssv for 34 bucks. It's where I got mine. I messaged him last night explaining the issues with the unit I bought from him and he offered to send me a new unit. Real easy going guy to work with. If any of you are interested PM me for his account name (don't want to violate any rules here).


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## Grobbins48 (Oct 16, 2017)

Ph pen is in the mail to get here today to get a better reading, but I have been pushing my 55 gallon to about 25cc/min now. Getting better pearling and now issue with the fish. I'll update this post once I have some more solid numbers.

Bump: Ph pen is in the mail to get here today to get a better reading, but I have been pushing my 55 gallon to about 25cc/min now. Getting better pearling and now issue with the fish. I'll update this post once I have some more solid numbers.


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## Edward (Apr 11, 2005)

So far I have seen posted these flow rates:

135 gal, 30 ccm, 24/7
134 gal, 80–100 ccm
125 gal, 60 ccm, with sump
125 gal, 10 ccm -> 1.13 pH drop, 15 ccm -> 1.80 pH drop 2 bps, 24/7
120 gal, 60 ccm
120 gal, 44 ccm
80 gal, 75 ccm, with sump
75 gal, 38 ccm
75 gal, 35 ccm
75 gal, 30 ccm
75 gal, 20 ccm
65 gal, 25 ccm
50 gal, 30 ccm, 5 bps

I have tested the RMA-151-SSV, 5-50 cc/min Flow Meter as the most recommended model and have to say it is really great equipment to have. The input pressure is 18 psi, output to a small check valve and then open line inside an Aqua-Medic CO2 Reactor 1000 placed three feet under the aquarium water surface. Here is the result:










How can I control injected CO2 quantity?


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## Wobblebonk (Feb 13, 2018)

I have an 80 gal with a 40 gal sump (with about another 25g of water in it) running @ 75 cc/min at roughly 20psi :/ and a 120 and 75 with sumps I have no idea the flow rate on, just has a nice metering valves but uses a ph monitor to cut off the co2 @ 1.2ph drop. and a 75 @ ~35 cc/min with no sump.


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## PlantedRich (Jul 21, 2010)

From lots of reading of posts, I feel there is no real way to say how much each tank will need. That leaves me to suggest doing a small check on your tank before adding any flowmeter as that gives you a better shot at getting the one that fits you best. 
It is not hard at all to check how much CO2 you are currently adding before buying the flowmeter. If you are set up, figure a way to stick a loose end of your CO2 input tubing up into an overturned test tube, etc. which you know how much it holds. Run the normal flow for some amount of time and do a little math to figure which flowmeter will give you a good reading in that range. 
And to help with all that math, there are lots of conversion gizmos on the net. No need to strain the brain converting CC per minute to cubic inches per hours when all we need is looking for the right conversion gizmo.


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## Edward (Apr 11, 2005)

Edward said:


> RMA-151-SSV, 5-50 cc/min Flow Meter


 Post #41 link fixed.


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