Resource Guide to choosing the right needle valve for precise control of CO2

[Marcel G]

I originally wanted to put it all here, but since I also made an online calculator of flow rate and since it is possible that I will have to update some of the data in time (which will not be possible here after some time), so I finally made an article on my website and I am just putting a link to it and few pictures here (for a better idea). I hope this will help others in choosing a suitable needle valve for their CO2 setup.

PS: This is basically an updated (and hopefully slightly improved) version of Bettatail's post on PlantedTank.net.

URL: golias.net/akvaristika/valves.php







Detail of one of the valves, including technical documentation for download:

 

[Yugang]

Really impressive work @Marcel G , thank you for posting.

Using overflow mode, I am not likely to buy a quality regulator but I do still have an interest in opportunities to advance technology in our hobby - especially if it can be done at a low price and improved functionality for our hobby.

Some may disagree, but my opinion is that CO2 stability is all that counts and I am not really interested in small adjustments as long as I know that my injection and CO2 ppm are stable. In a thread that was deleted on UKAPS I argued that we would best have some cheap gas nozzles (just a hole in a piece of metal), with calibrated hole sizes to meet our CO2 flow target.
Example in case may be diesel engine fuel injectors, which can have really small holes (80 micrometers and smaller) and can be mass produced and purchased at reasonable price. We could get stability for a good price, and would not have to worry anymore about (semi) professional regulators (usually several hundreds of USD for a good needle valve / regulator).
Another option, if the above does not work, may be ceramic, "leaky", materials but these may not be mass produced off the shelf and therefore expensive.

Anyone interested could use @Marcel G methods for calculating some typical regulator / nozzle hole sizes and look up if there may be any aftermarket fuel injection nozzles that could be used for our hobby.

 

[Marcel G]

Some may disagree ...

I don't!

I totally agree with you, Yugang, and I myself use a CO2 diffuser with overflow in my experimental aquariums according to your suggestion (for which I will never stop being grateful enough).


PS: At 0:23 you can see the excess gas "overflow".

However, other reasons than promoting fine needle valves led me to study this issue and subsequently write this article.

The first reason was that the vast majority of aquarists do not use a „true CO2 diffuser“ [as I call it] (either because they already use another method of dissolving/dosing CO2, or because they simply do not understand the principle of a true CO2 diffuser and its benefits).

The second reason was that even when I use a CO2 diffuser myself, I'm dealing with the problem of too high flow (due to the inability to adjust less due to the use of inappropriate needle valves), which causes the gas in my cylinder to run out disproportionately early, resulting in the unnecessary cost of early CO2 cylinder replacement. P.S. Not everyone (especially in Europe) has a car and can drive to fill a CO2 cylinder at a filling station. For example, I myself use small CO2 bottles designed for SodaStream (soda maker), which I can exchange at the local store for full ones. But exchanging them (compared to filling standard large CO2 cylinders) is quite expensive. Then when I run out of a bottle like that in 45 days instead of 90 days, it's a money suck (especially when you have more than one).

You can find many threads on forums about which needle valve to get, and very often there is a preponderance of subjective user preferences (which is not good). In our small European country, for example, there is practically only one aquarium forum where Camozzi needle valves (with a flow rate of 55 ℓ/min) are considered the pinnacle of finesse and precision. An aquarist (newbie) who is not familiar with it at all and reads the thread on valves here will get the impression that he will do best to get this valve. Yet the comparison I made shows that this is basically the worst option (if you leave out of the comparison the various no-name valves that tend to be part and parcel of most cheap CO2 kits, which boast "super extra fine" valves whose orifices are about as narrow as the underwater Channel Tunnel connecting France to England).

If someone wants to use a CO2 diffuser, then they can get by with that Camozzi valve (or even worse one), but if they need to restrict the gas flow to a minimum (to make their CO2 cylinder last as long as possible), then I'd recommend a valve more in the "good" category. If someone uses a valve for conventional CO2 dosing methods, and thus needs more precise control (more precise dosing), then he should definitely think about valves from the "excellent" category (for nano aquariums) or "very good" / "good" (for larger aquariums). A lot of aquarists take the choice of needle valves lightly because they don't give much thought to the potentially negative effects on aquatic critters. I can't tell you how many posts I've read about how some novice aquarist poisoned all his fish/shrimps due to a poorly set flow rate. And we can certainly agree that using a valve in the "good" category is certainly better at setting the correct flow rate than using a valve in the "unsatisfactory" category.

Of course, I'm more than sure that it will have virtually no effect on most aquarists (since most people rarely change their minds), but it may help a few people, just as it helped me.

 

[Yugang]

I myself use a CO2 diffuser with overflow in my experimental aquariums according to your suggestion

I like your implementation of CO2 Spray Bar, it looks really clean in the tank. The bubble from the overflow could be a bit smaller, but if you don't care about a little extra CO2 consumption you will have the benefit of optimal CO2 stability.

However, other reasons than promoting fine needle valves led me to study this issue and subsequently write this article.

I thought it would be good to document my idea in your thread, as it got deleted on UKAPS, but most importantly I really like your detailed and original study of needle valves.

I'm dealing with the problem of too high flow

We may start with the question if we really need the high CO2 ppm that is now generally accepted and advised in the hobby. I am now doing 10 ppm on my 50 gallon tank, and with about 1 bubble per second 24/7, my CO2 tank will last for about a year. I have not yet discovered the downsides.

I suspect that if we would make a clean start with the hobby, forget all the legacy and commercial interests, we would never end up with expensive needle valves for CO2 adjustments. Some people started to use technology three decades ago, from a pragmatic perspective, then some others created narratives and/or got commercial vested interests. With a clean sheet, and thinking from the requirements of a planted hobby tank, we would not want to adjust at all, as that gives the best stability and cost savings. Now that the hobby has got its own traditions, it may take time for more rational approaches to be accepted.

Of course, I'm more than sure that it will have virtually no effect on most aquarists (since most people rarely change their minds)

 

[bizovski]

@Marcel G. ... I buy my co2 in Croatia for like 30eur 10kg bottle .... It lasts 6 months for me. Using sodastream bottles seems very expensive to me. Can't you get your co2 bottle get delivered to you. We have that service here. Welders and car repair shops use it. They come and swap the bottle. It's a bit more expensive than where I fill my bottle, but not that much.

I struggled with cheap chinese valves for a while. Saw those expensive ones swagelok, parker, but was to cheap to give 100+eur for a valve. So i bought that Camozzi. And I'm happy with it.

 

[Marcel G]

We may start with the question if we really need the high CO2 ppm that is now generally accepted and advised in the hobby ...

The way I see it, from a plant perspective, certainly no more than 10 ppm CO2 is needed. I myself now use about 15 ppm in my experiments. I do plan to do one experiment to compare the growth rates of selected aquarium plants at different CO2 concentrations (e.g. 7, 15, 30, 60 ppm), but now I want to complete another experiment that will take a few more months.

One thing, however, may be of some importance when using high concentrations of nutrients (including CO2), and that is their potential negative effect (toxicity?). I don't want to stir up a debate here about the harmlessness vs. harmfulness of high nutrient doses, but I have observed in my own experiments that while certain nutrient combinations (and most likely pH) are preferred by algae, others are disliked for some reason. So it is [purely theoretical] possible that high doses of CO2 (and other nutrients) can suppress certain algae/bacteria species under certain circumstances. This would explain why some aquarists experience algae blooms at low nutrient concentrations, whereas algae recedes at higher doses. There may be more factors that play a role in this, of course, but nutrient concentration may certainly be one of them. I myself have noticed on several occasions that in certain aquariums where I have had much higher concentrations of certain nutrients, for example, the water (compared to other aquariums) has been clearer. So I think we should take this into account as well.

So, I myself am convinced that plants need really small amounts of nutrients (including relatively small amounts of CO2 ... under 10 ppm) to grow well, BUT we need to figure out how to keep algae/bacteria at bay [under these conditions]. Many "challenging" plants can grow well without artificially added CO2, BUT they grow very slowly, making them much more susceptible to algae overgrowth. Plants in "slow growing mode" (i.e. plants supplied with low light and nourished only by natural CO2) must therefore be kept perfectly clean, otherwise they will be covered by algae and stop growing and die. This problem does not need to be solved for plants in "fast growing mode" (i.e. plants supplied with strong light and nourished by unnaturally high CO2 concentration) => these plants will "escape" the algae.

 

[Marcel G]

Can't you get your co2 bottle get delivered to you. We have that service here. Welders and car repair shops use it. They come and swap the bottle. It's a bit more expensive than where I fill my bottle, but not that much.

If you're lucky enough and live in a bigger city, this is an option. But in smaller towns or villages, you're out of luck (= my case).

I bought that Camozzi, and I'm happy with it.

I too now use Camozzi (RFO 352-M5) for my four nano aquariums that are supplied with CO2 (the other four are not), but I don't share your satisfaction. The slightest turn of the valve totally throws off my flow setting. Going from 1 bubble per second to 2 bubbles per second is a half hour job of constantly turning the valve back and forth and finding out "that was already too much". In large tanks this may not be such a problem, but only if you're not so concerned with correct/accurate dosing ... which is unfortunately the case for most aquarists [in my opinion]. I get it (which is also why I said most aquarists won't want to deal with it), but I don't want to be like that and neither can I be (with respect to aquarium critters). But please don't take this as a rebuke or an attack on my part. I am only offering my limited knowledge here. If you find it useless, there is nothing easier than to let it go.

 

[bizovski]

I'm in range of 9-12 bps on my Ista intense flow bubble counter. And I fine tune it with my slow motion camera.

Have you maybe taken a look at aliexpress gas metering valves ? LZB-3W. But I'm not sure how much pressure they can take (it says 0,2MPa, and that is maybe not enough for a ceramic diffuser).

 

[Marcel G]

I'm not sure how much pressure they can take (it says 0,2MPa, and that is maybe not enough for a ceramic diffuser).

What matters with our needle valves is not the maximum pressure, but the flow rate (stated in CFM, l/min, dm3, etc.). Most valves are designed for pressures we have no chance of achieving in our hobby (e.g. 3000 psi = 207 bars). More important, then, is the diameter of the orifice combined with the orifice needle that screws into it, which together determine the maximum amount of gas that can flow through the valve in a given unit of time. You can think of the orifice as a tube. The larger the diameter of the tube, the more gas will flow through it [e.g. per minute]. By turning the needle, you plug or unplug the tube. So a valve with the thinnest possible tube (orifice) and a long narrow needle is ideal, because it is then able to pass only a small amount of gas (and in small increments). In aquaristics, we need the valve to pass gas at a maximum of tens to units of litres per minute. A Camozzi valve at full open will pass 55 litres/min, which is too much. Yes, it can be screwed down so that only those few litres per minute flow through it, but every slight turn means a significant increase in flow. So it's not suitable for fine control. I think that valves like this are only used in our hobby due to the cunning of vendors and the ignorance of aquarists. Aquarists just want CO2 and they want it cheap. So the vendors will help them fulfill that wish (even at the cost of totally inappropriate components).

 

[bizovski]

I was talking about metering valves (flow meters), not needle valves. Maybe you got me wrong. They have max working pressure.

GreggZ was talking about them and using them. But some other brand. They are around 30eur on ali.

But these are according to my quick math only good for larger tanks. 1 bps would be around 2-3 cc/min. And those are 6-60 cc/min. The finest one.

 

[Marcel G]

That doesn't look bad, but it's hard to judge without trying it out.
PS: Yes, 60 bubbles per minute = 1 bps (4 mm in diameter) equals to 2 ml, so unfortunately this is unusable for nano tanks.