Pressurized CO2...Just thought I'd share.
So, there have been a lot of threads (it seems) lately regarding pressurized CO2. Hopefully, this primer will help alleviate any fears that people have when starting to delve into CO2 as it can be quite intimidating at first. In addition, hopefully this primer will answer some of the most commonly asked questions regarding pressurized CO2.
As this thread will be discussing how to set up a pressurized CO2 system, advantages/disadvantages of using a pressurized setup versus a DIY (yeast) CO2 system will not be discussed in this primer. For more information, please take a look here:
On to pressurized CO2!
First, when people refer to pressurized CO2, we often read that we will need a "regulator" or a "regulator build." What does this mean exactly? This term is thrown around quite loosely in the aquarium hobby, but a pressurized CO2 system consists of more than just a regulator.
Here are the essential components you will need:
1) A CO2 cylinder
CO2 cylinders come in various sizes. They are often used in paintball guns (usually sold as 20 oz cans). They also come in 2.5, 5, 10 and 20 lb sizes (larger sizes such as 50 lb tanks do exist, but they are quite large and bulky, and are not commonly sold outside of specialty applications).
CO2 tanks come with a fitting known as a CGA320 fitting, which is standard in North America. Europe and Asia use different industrial standards. Paintball tanks, however, do not come with this fitting, and come with a pin depression type valve. More on this will follow below.
Many people believe that getting a small, paintball CO2 tank is "cheaper", however, this is not usually the case. Regulators (see below) often come with CGA320 fittings (or can be adapted to such). However, as paintball tanks do not contain this CGA320 fitting, normal regulators cannot be used, and you must purchase either a special regulator with the required fitting, or look around for a paintball tank to CGA320 adapter (often, quite difficult to find). In addition, refill costs for CO2 tanks are generally not much different. The refill cost for (say) a 5 lb tank and 10 lb tank may only be a few dollars different. For example, I can get my 10 lb tank refilled for $17.50, while a 20 oz paintball tank may cost $5 to refill. This means that the cost per pound of gas is more for a smaller tank. In addition, the larger the CO2 tank, the longer you can go without refilling the tank, etc. It can be quite a hassle to drive out and refill the tank, depending on where you live. The general piece of advice is to get the largest tank that you can afford and/or is feasible for the space that you have.
The next piece of essential equipment we will require for a pressurized CO2 setup is the regulator.
A regulator takes the tank pressure of the CO2 tank (normally at ~850 PSI or more, depending on the ambient temperature) and reduces it to a lower pressure.
We normally look for a regulator with two gauges. This means there are two pressure dials. The first pressure dial (high pressure dial) will indicate the pressure in the CO2 tank (i.e. the amount of CO2 that is remaining in the tank). The second pressure dial (low pressure dial, also known as the delivery pressure), will be the pressure that the regulator is bringing the CO2 down to. This is usually set anywhere from 5-20 PSI, depending on the size of your tank, and the desired bubble rate.
Sometimes, we also here the term dual stage used. Note that dual stage and dual gauge are not the same. These terms are sometimes used interchangeably, but this is incorrect. Dual stage refers to an additional body within the regulator that allows the pressure to be dropped in two stages, hence the name. Here are two figures that show the differences between the two:
Single stage regulator:
Dual stage regulator:
As the finer details are beyond the scope of this primer, more information regarding the differences can be found over at the Barr Report, where Left C and I are quite active as well.
There has been a lot of debate over whether a single stage regulator or a dual stage regulator is best. There are often stories about people encountering "end of tank dump" (when the CO2 tank pressure begins to drop, there is sometimes a phenomenon in which all the CO2 will suddenly rush out of the tank, ending up in your aquarium and subsequently gassing all your fish to death) when using a single stage regulator. Some people will blame this on the regulator, while others will point out that it was a combination of a single stage regulator and a poor needle valve. Yet others will point out that despite having a single stage regulator and a sub-standard needle valve, they have yet to encounter "end of tank dump".
In the end, whether you purchase a single or dual stage regulator is up to you; dual stage regulators are the "premium" regulators, and will work reliably for our purposes. Single stage regulators will also work well for our purposes, and are often cheaper than dual stage regulators (more on this later).
Some good brands that I recommend:
Single stage regulators:
Dual stage regulators:
Finally, when purchasing your CO2 regulator, regardless whether it is a single or a dual stage regulator, be sure that you have the correct fitting (CGA320), or else it will not fit the CO2 tank. Sometimes, you may be able to find cheap regulators on eBay (more on this below) that do not have the correct fitting (most commonly found are those with a CGA580 fitting, used for nitrogen ). If this is the case, you can take off the fitting and replace with the appropriate CGA320 fitting.
3) Needle/Metering Valve
The next piece of equipment that is essential is the needle/metering valve.
A needle valve is a piece of equipment that takes the delivery pressure of the regulator and further drops the pressure down to the very fine flow rate that we require for aquarium purposes (i.e. we often refer to our flow rates as "bubbles per second"). A metering valve is the "high end" needle valve.
Needle valves work by restricting the flow of gas via a small needle (hence the name) that can be opened/closed via a screw/caliper handle. In general, higher quality needle valves/metering valves will have allow finer control by having more threads. This means that it takes more turns of the handle to change the flow of CO2, meaning you get finer resolution (i.e. if you turn a needle valve 1 turn and get an increase from 1 bubble per second to 10 bubbles per second, you would have a hard time adjusting your flow. However, if you turn another needle valve 1 turn and only get an increase from 1 bubble to 2 bubbles per second, you can achieve much finer control).
A good quality needle/metering valve is essential. This is definitely one piece of equipment you do not want to be stingy on.
Here are some brands that I recommend:
Fabco (particularly the NV55)*
Ideal (particularly the 52-1-11)**
Swagelok (many various models available)
Parker (also many various models available)
For those that are more technically inclined, have a look at the thread over at the Barr Report (linked above), as it discusses the finer points of a quality needle/metering valve (i.e. best Cv to look for, etc)
One brand of needle valve that I would strongly advise against is the Clippard needle valve (Part #: MNV-4K2) . While it is quite cheap (perhaps $18, if ordered online), many users have lamented that the quality of this particular needle valve leaves much to be desired. A common problem with this needle valve is that it "floats." This means that while you set the CO2 flow rate to a particular setting one day, the next day (or perhaps within a few hours!), the CO2 flow rate will change noticeably, requiring more fiddling on your part. This means that while you set your CO2 to an "optimal" flow rate one day, the flow might stop the next day, or it might be so high that it will gas all your fish to death. Definitely, this is something you want to avoid, so do not be stingy on a quality needle valve.
*Note 1: The Fabco NV55 contains #10/32 port fittings. These are not your standard fittings and adapters cannot be purchased at the hardware store. The setup I would recommend is to have #10/32 to hose barb fittings and not trying to find #10/32 to (say) 1/8" NPT adapters. This is because attempting to attach the Fabco NV55 to the regulator is not a good idea. The Fabco NV55 is quite a heavy needle valve, and the #10/32 fittings are quite small and fragile, so a slight bump may cause the fitting to break. With the hose barb adapters, you can run this needle valve in-line.
**Note 2: This particular Ideal metering valve has 1/8" female NPT ports on both ends. Other models exist, and I can also forward you the PDF/website with the particular details if you require/PM me.
"Optional" (?) Parts
Here now, are the optional parts of a pressurized CO2 setup. While the aforementioned CO2 tank, regulator and needle valve are absolutely essential, the following pieces of equipment, while totally optional, are highly recommended.
5) Bubble Counter
7) Drop Checker
8) Miscellaneous equipment (check valve, airline tubing)
9) "Luxury" items (pH controller)
Let us begin with 4) Solenoid
A solenoid is an electronically controlled valve that opens/closes depending on whether electricity is flowing through it or not. For pressurized CO2 purposes, we normally use a "normally closed" solenoid. This means that when there is no electricity, the solenoid is closed, and no CO2 flows. When there is electricity, the solenoid is open, and CO2 flows.
A solenoid provides the option of putting your CO2 onto a timer and/or a pH controller, so that your CO2 will turn on/off automatically. This is beneficial, as it can prolong the amount of time your CO2 will last (i.e. rather than having it on for 24 hours, you can turn it off at night, when plants are no longer photosynthesizing).
Here are some good solenoid brands that I can recommend (in no particular order):
Burkert (Model #: 6011)*
Clippard (Model #: MME-2PDS-D110)*
Fabco (Model #: 3853-04-A287)*
Of these 3, the Clippard is the only one (as far as I know) that has the handy feature of having a red LED that indicates when the solenoid is open, and CO2 is flowing. However, many users have reported that the solenoid does get quite warm (sometimes to the point where you cannot leave your hand on it comfortably). The other three brands do not seem to have this overheating issue, but also do not possess the same LED.
Most solenoids run ~$20-30, but you can easily find a cheaper solenoid on eBay (see below and/or PM me for the actual link...)
*Note: These model numbers are for solenoids with a 1/8" female NPT ports on either side. If you wish to have different port sizes, I can forward you the PDF with the appropriate information.
5) Bubble Counter
The next piece of equipment we will discuss is the Bubble Counter.
A bubble counter allows us to easily determine the flow rate of the CO2 that is going into the aquarium. We often refer to the flow rate as "bubbles per second." The bubble counter is filled with fluid (it can be water, glycerin, or even mineral oil. The latter two are sometimes preferred because bubbles flow through the liquid slower, making it easier to count. In addition, they do not evaporate like water does), and as gas flows through, bubbles are generated so that you can count your bubble rate.
Many different types of bubble counters exist, from in-line ones, to DIY ones, to commercially bought bubble counters. They all perform the same function, at different costs. Some people prefer one over the other due to aesthetics, size constraints, etc., but in the end, they perform the same function.
Not much else to say on this piece of equipment ;)
6) Dissolution Methods
An effective method of introducing CO2 into your tank is required. If CO2 bubbles are reaching the surface of the water in your aquarium, then much of it is being lost and you are not getting CO2 dissolved into your water column.
There are various pieces of equipment (listed below) that will help aid in diffusing CO2 into the water. They all aid in the dissolution of CO2 to differing degrees. Whether you use one or not is not important; the important point is being able to get CO2 into your water.
From my previous article, I will just copy/paste the various methods of getting CO2 into your water:
1) Bell Diffuser: A passive method of CO2 diffusion, this relies on the assumption that CO2 will dissolve into the water column faster than the CO2 is produced (not likely). Not an effective method of introducing CO2 into the aquarium.
2) Feeding the CO2 tube into a filter intake: Slightly more efficient, this method allows the CO2 bubbles to be fed into the intake of a filter, allowing the bubbles to be chopped up by the filter impeller. Be warned that this method is said to shorten the lifespan of the filter impeller.
3) Commercially available "bubble ladders": Hagen makes a product that is known as "bubble ladder". This product allows CO2 bubbles to travel a long a track, allowing the CO2 more time to dissolve into the water column. The ladder is quite large and bulky (in my opinion), and some people may find it aesthetically unpleasing.
4) Ceramic disc diffuser: Typically a glass diffuser that contains a ceramic disc with miniature pores. These diffusers were first made by ADA (Aqua Design Amano). Such diffusers rely on the small pores on the ceramic disc to adequately create mini-CO2 bubbles, vastly increasing the rate of CO2 dissolution in water.
5) Inline CO2 reactor: Most arguably the best method of CO2 dissolution, the inline CO2 reactor is inline with a (canister) filter output. Using this method, the CO2 is very effectively dissolved.
7) Drop Checker
Most likely the newest addition to measuring CO2 levels, a drop checker consists of an airspace between the liquid inside the drop checker and the water in the aquarium. Carbon dioxide readily diffuses outwards from water into the air; as such, the carbon dioxide in the aquarium will readily diffuse into the airspace in the drop checker. The liquid inside the drop checker contains a solution of known kH (i.e. 4 or 5 dkH) with an indicator (bromothymol blue (BTB)) which serves as a good indicator of CO2 dissolution. The CO2 that is in the airspace of the drop checker will readily diffuse into the drop checker solution, changing the colour of the BTB indicator.
Different drop checkers exist today. Red Sea makes one, ADA makes one, Cal Aqua makes several, some can be found on eBay etc. Of course, you can also DIY one yourself. They all work essentially the same, and perform the same function. Some people prefer one brand over the other due to aesthetics and/or ease of comparing the colours.
Here are some instructions for making your own DIY drop checker.
In addition to a drop checker, a reference solution is required when using a drop checker. This is usually a 4 dkH reference solution, but it can also be a 3 or a 5 dkH reference solution. The different dkH reference solutions will turn green (in the presence of BTB) at different CO2 levels (for example, the 4 dkH reference solution turns green at 30 ppm of CO2).
Sometimes, you may find instructions that come with purchased drop checkers to use aquarium water, distilled water, or even tap water. These instructions are incorrect and should be ignored. If you do not use a reference solution, you will get incorrect results when using a drop checker.
Many people (mistakenly) believe that the pH/kH/CO2 relationship is the end-all for measuring CO2 levels. They believe that by measuring the pH and kH of the aquarium water, they will know their CO2 levels. However, this is not the case.
The pH/kH/CO2 relationship can only be used if carbonates are the only buffers in the water. However, in the aquarium, there are other factors that will affect this kH reading (such as phosphate buffers). As a result, the pH/kH/CO2 relationship cannot be used with tank water, tap water, or distilled water.
When making a dkH reference solution, we are only adding carbonates to the water, so only here can we make valid conclusions using the pH/kH/CO2 relationship.
Instructions for making your own 4 dkH reference solution are also in the link above :)
8) Miscellaneous Equipment (Check valve, airline tubing)
Here, we will cover miscellaneous equipment (this maybe considered essential!)
a) Check valve
Placing a check valve is important to prevent a back siphon from occurring. If water were to back siphon, it could go back through the needle valve, destroying your regulator diaphragm. To protect your investment, a check valve provides good protection for a few dollars.
Plastic check valves work fine, but will harden with time (the CO2 makes the plastic brittle), rendering the check valve useless. It is worthwhile to invest a bit more in a brass check valve, as these will not become brittle like their plastic counterparts.
b) Airline tubing
Of course, without airline tubing, you would not be able to get the CO2 from your CO2 tank into your aquarium, so it goes without saying that you will require airline tubing.
The type of tubing does not really matter. I have used your standard vinyl airline tubing as well as your standard silicone airline tubing. Both work fine for our purposes. Some people will point out that silicone tubing is thousands of times more permeable to CO2 than other types of material (there is a website out there with a table showing permeabilization of the various materials). However, given the low pressures at which we work, and the relatively short distances of tubing (say 10-20 feet, at most), the amount of CO2 gas that is loss through silicone tubing is negligible.
While you can purchase CO2 resistant tubing, I find this to be an unnecessary expense.
We can actually do some calculations to see how much CO2 is loss when different types of tubing are used.
Let's crunch some numbers. All data is taken from the following site
Silicone has a permeability of 20,132 (cc-mmsec-cm2-cmHg) according to that table. Note that the units are as follows:
cc-mmsec-cm2-cmHg - the flow of a gas in cubic centimeters per second per area in cm2 through a thickness in mm which has a pressure difference in cmHg
Also, that the magnitude is to the -10 magnitude (important!)
Typical OD of silicone tubing is 5 mm (3/16") with an ID of 4 mm, so a wall thickness of 0.5 mm.
Let's assume the length of the tubing is 100 cm (1 metre). We can calculate the surface area (top and bottom of the tubing's surface area (the ends) is essentially negligible in this calculation). Using the above length, we get a surface area of 157.47 square cm.
Typical pressure is 30 PSI, or 206.84 kPa. Standard atmospheric pressure is 101.3 kPa, meaning the pressure difference is 105.54 kPa or 76.16 cmHg.
Let's assume this is over 1 second.
So now, we have all the necessary values to substitute into the equation.
20,132 cubic centimetres of CO2 (to the -10th magnitude) is lost over a surface area of 1 square centimetres, with a wall thickness of 1 mm, over 1 second, with a pressure differential of 1 cmHg.
Thus, over 157.47 square cm, with a wall thickness of 0.5 mm, over 1 second, with a pressure differential of 76.16 cmHg works out to be:
120,720,684 cubic centimetres (to the -10th magnitude). This works out to be 0.012 (rounded) cubic centimetres (mL) of gas per second.
Now, to put this in real world terms. A 10 pound cylinder of gas, coming out at 30 PSI, at 25C works out to be 1235.51L of gas (10 pounds works out to be 103.09 moles).
Assuming you keep your CO2 on for 8 hours a day, you are losing 345.6 mL of gas a day, or about 0.028% of your gas per day (over 1 metre of tubing).
Using similar calculations for vinyl tubing, you get a loss only 6.18 mL of gas per 8 hour day, over 1 metre of tubing. Tygon (for food/beverage, according to the Cole Parmer site) yields slightly better results at 4.63 mL of gas per day, over 1 metre of tubing.
So, even in the worst case scenario with silicone, you are losing a negligible amount of CO2.
9) Luxury Items
The last part covers what I consider to be "luxury" items, or completely optional parts (unlike the above).
A pH controller (such as those made by Milwaukee) will allow you to determine the pH of your aquarium water on a continual basis. By hooking up the pH controller to a solenoid (which is part of your CO2 system), you can have your pH controller inject CO2 when your pH goes above a certain set point, and have it stop injecting CO2 when your pH drops below a certain set point.
In my opinion, this is completely unnecessary. I believe too much emphasis on aquarium fish requiring the "perfect pH" has been placed in our hobby, leading beginners to believe that certain fish can only be kept at a pH of 6.4, or 7.0, etc.
Perhaps if you are keeping extremely sensitive fish, with very exacting water parameters required, would I see a need for a pH controller. The cost of the controller, probe and the calibration solutions are also quite expensive, but if cost is not an issue for you, then this may be a piece of equipment you would want to consider.
Pre-built setups versus building your own
Here, we will discuss pre-built regulators versus putting your own pressurized CO2 system together.
Various pre-built regulators exist on the market today. Most commonly seen are the Milwaukee, Azoo, and JBJ pre-builds. These often come with the regulator, solenoid, needle valve, and perhaps a bubble counter, and are often quite cheap.
However, the one complaint that many users have with these pre-built pressurized CO2 setups is that the stock needle valve "floats." As mentioned before (see the section on needle valves), floating occurs when you set a particular flow rate, but it changes due to the poor construction of the needle valve.
Quality pre-built pressurized CO2 setups do exist, however.
Another way to obtain a pressurized CO2 setup is to build your own setup from parts that you buy separately and piece together yourself. While this method may seem more laborious, requiring you to buy the parts individually, do research, etc., it may save you money in the long run. This is especially true if you wait for the best deals that pop up on eBay and/or Swap and Shop forums. At the very least, you may be able to get "better" parts for the same price as one of the pre-built pressurized CO2 systems.
Putting it All Together
Here, I will discuss how to put everything together. Hopefully, I will have some instructive images as well.
The setup I will be describing is as below:
The general design is as follows:
CO2 tank -> CO2 Regulator -> Solenoid -> Needle valve -> Bubble Counter -> Diffuser
Some points to watch out for:
Between the CO2 tank and the CO2 regulator, you will require a washer to prevent leaks. This can be a disposable (one time use) nylon washer, or a perma-seal. Sometimes, you can get a nylon washer for free when you get your CO2 tank refilled (just ask!)
Between the regulator and the solenoid: Ensure that the fittings match (i.e. 1/8" to 1/8", or get the necessary adapters. Adapters can be bought for a few dollars at Home Depot and/or Rona.
Between the solenoid and the needle valve: Again, ensure that the fitting sizes match. If they don't, you can buy the necessary adapters at the hardware store.
Between the needle valve and the bubble counter: Again, the same rule as above applies.
Finally, for all connections: You will require either teflon tape or pipe compound (sometimes called pipe dope) to ensure that all the connections are well sealed. I do not recommend teflon tape before the solenoid as there have been reports of people getting small bits of teflon tape lodged within their solenoid, preventing it from closing all the way (this means CO2 will still flow!). As such, I recommend pipe compound instead (this can be bought from the hardware store for a few dollars as well). Use it sparingly, and don't use it excessively.
After putting the entire setup together, be sure to check all the connections for leaks using soapy water. By brushing/spraying the soapy water onto the connections, you will be able to detect any leaks due to the formation of tiny bubbles.
Some Final Basics Instructions
Finally, some basic instructions on how to use your pressurized CO2 system now that you have everything hooked up.
1) Ensure that a nylon washer is between the CGA320 nipple and nut (A).
2) Screw the nut (A) onto the CO2 cylinder. Tighten with an appropriate sized wrench.
3) Unscrewing the bubble counter nut (I), thread the rubber O-ring through airline tubing, and then attach the tubing to the barb. Take this opportunity to fill the bubble counter with water (other options include mineral oil or glycerin; the choice is yours). Screw the bubble counter nut back into place.
4) Ensure that the regulator pressure adjustment knob (B) is turned counter clockwise until there is no resistance. This ensures that the low pressure gauge (E) is not destroyed when the CO2 cylinder is first opened.
5) Open the CO2 cylinder valve (C).
6) The high pressure gauge (D) should read ~800 – 1000 PSI, depending on the level the CO2 cylinder is filled, ambient temperature, etc.
7) Turn the metering valve adjustment knob (G) clockwise until you feel resistance (this will close the metering valve to restrict gas flow). Do not overturn, as we will now reopen the valve (counter clockwise) to allow gas to flow.
8) Plug in your solenoid (F).
9) Slowly turn the pressure adjustment knob (B) clockwise, until the desired working pressure is reached. In this image, the working pressure is set to ~5 PSI. Gas should begin to flow and you should see bubbles in the bubble counter.
10) Adjust your needle valve (G) so that the desired flow rate is achieved.
Useful Glossary of Terms
If you can think of any more, let me know!
Bubble Counter: A piece of equipment that allows you to determine the flow rate of your CO2 in "bubbles per second". Optional. Can be made DIY or bought commercially.
CO2: Carbon dioxide. Plants require carbon in order to grow, and carbon dioxide is provided as a carbon source.
Delivery Pressure: Also known as the working pressure. This is the pressure that is indicated by the low pressure gauge. Standard delivery pressures vary from 5 - 20 PSI.
Drop checker: A piece of equipment that will help determine whether optimal levels of CO2 are being reached. Optional. Can be made DIY or bought commercially.
Dual gauge: A regulator that has two pressure gauges (two manometers). One pressure gauge will indicate the pressure in the CO2 tank, while the other gauge will indicate the delivery pressure.
Dual stage: A regulator that has two stages of pressure regulation. c.f. single gauge and single stage.
End of tank dump: A phenomenon whereby the remainder of a nearly empty CO2 tank will empty its contents into the aquarium.
Metering valve: See needle valve.
Needle valve: A piece of equipment that further drops the delivery pressure so that even finer control of CO2 flow can be achieved.
pH controller: A piece of equipment that will measure your aquarium water pH and inject/stop injecting CO2 as the pH rises above a set point/drops below a set point, respectively. Optional. Requires a solenoid.
Regulator: A piece of equipment that drops the CO2 tank pressure to a much lower delivery pressure.
Single gauge: Refers to a regulator with only one pressure gauge (manometer). Will indicate the delivery pressure.
Single stage: A regulator that only contains one stage of pressure control. c.f. single gauge and dual stage.
Solenoid: An electronic switch that will open/close depending on whether electricity is flowing or not. Will allow you to put your CO2 onto a timer, so that you can turn it on/off automatically. Is required when using a pH controller.
Working Pressure: See Delivery Pressure
Excellent writeup. Thanks for sharing!
this helped me alot!
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