CO2 Spray Bar - a summary

[Zeus.]

I have only had a quick read through the thread, plus I do remember your posts elsewhere, I have to admit I am also impressed and would give a CO2 spray bar serious consideration in next tank. One less thing under the tank and seems very straight forward.

The only downside I can see is the CO2 spray bar limits ease of access to plants. Impressed with the pH drop speed also. quickest I ever had with my 500L was about 20mins for a 1.4pH drop- but that was with twin injectors reactors

 

[Koan]

Surprisingly, even though I posted earlier about the CO2 Spray Bar than the reactor, this has not gained much traction yet.

For my part @Yugang, the issue is that adding any new large distracting hardware inside the tank is a step backwards.

I'm sure the math is quite simple, but I wonder about the logistics of making these using 1/2" acrylic pipe, so that this spray bar is on the same dimensions as other Lily pipe hardware? Seems like it could be done but maybe it would require a Dremel cutting wheel, or maybe a table saw or something.

 

[Yugang]

For my part @Yugang, the issue is that adding any new large distracting hardware inside the tank is a step backwards.

That's a fair remark, and was also the main concern that people gave when posted on the other forum. I would consider it an alternative for in tank diffusers, not so much for external reactors. However, my SprayBar on a 50 gallon tank is just 10 cm long, and if I like I could also have the main part of it above the water surface so that it is hardly visible in the tank.

I am now for more than a month testing how my tank does at 15 ppm, stabilised by the CO2 Spray Bar. As for the CO2 Spray Bar in overflow mode the only concern I have found is that it does need a reasonable water flow, as stagnant water will not provide the stability of CO2 injection that we want to have. For the rest, I believe this is my setup for the next year to fully explore the pros and cons, and I couldn't be happier with how my tank is doing so far.

 

[Yugang]

It may be helpful to remember that we do not necessarily need the same design as I use, we don't need to find a transparent acrylic tube or do the DYI. The only essential part of the design is a constant surface area between water and CO2, and an overflow for the CO2. Besides that, we are almost unrestricted in the design of the Spray Bar.

Take the little box that is part of the 17 piece IKEA Pruta food container set, and it will work as well. IKEA sells the full set for about 5 USD.



I currently use 3.500 mm2 to push about 10-15 ppm on my 50 gallon tank. I use the design on he left in the picture.
The small IKEA box on the right measures 80*80 = 6.400 mm2, and could be made into an overflow CO2 Spray Bar by just mounting it upside down in the tank, with a CO2 tube leading to it. The only modification needed would be to cut or drill a small hole in the side, so that bubbles can escape for overflow mode and keep the surface area constant. When the box is above the water, only the walls just below the water line even less visible.

 

[Art]

So @Yugang this seems to be a similar concept to the old CO2 bells that we had that allowed for a gas bubble "burp" to clear out when too much gas. Your design is more streamlined and explains why/how it works. Correct?

 

[Yugang]

So @Yugang this seems to be a similar concept to the old CO2 bells that we had that allowed for a gas bubble "burp" to clear out when too much gas. Your design is more streamlined and explains why/how it works. Correct?

The benefit of CO2 Spray Bar is that it keeps CO2 stable with overflow mode, and is continuously refilled. The similarity with CO2 bells is that it uses a flat water/CO2 interface rather than bubbles. I am not a fan of the old bells because they were not stable - this is probably why they have nearly been forgotten and diffusers and bubble reactors became the standard.

 

[*Ci*]

I am working on a couple of co2 sparybars for my two tanks, and have a question, @Yugang
I want to mount them above and slightly in front of my water return spraybars as you have done, from these pictures on your old UKAPS thread:



How did you mount it? Suction cups won’t work in this position.

I guess your UKAPS thread was taken down at one point? It is there again now, in case you did not know:

CO2 Spray Bar

 

[Yugang]

I am working on a couple of co2 sparybars for my two tanks, and have a question, @Yugang

Always happy to help @*Ci* , nice that you give it a try. Let's keep in touch on PM as well, if the below is not clear enough.

How did you mount it? Suction cups won’t work in this position.

I drilled holes in the end caps, and used a screw to connect the caps of water spray bar and CO2 Spray Bar. In the photo on the left, looking through the hole for overflow, if you look carefully you can see the screw as well.
There is no need to connect the CO2 Spray Bar to the water spray bar, I currently also don't do that, but it is really important that the water under the CO2 Spray Bar has some flow. With nearly stagnant water the CO2 Spray Bar still works, but the absorption will be limited by diffusion in the stagnant water and be less predictable.

I guess your UKAPS thread was taken down at one point? It is there again now, in case you did not know:

I wasn't aware, and this is really good news. I have asked them to remove the end posts from the mods regarding the ban, as these were written long time ago when facts and emotions had gotten a little bit mixed up.
Perhaps a revitalised UKAPS will even reevaluate the bans of some former members and welcome also their former admin again.

 

[*Ci*]

I drilled holes in the end caps, and used a screw to connect the caps of water spray bar and CO2 Spray Bar. In the photo on the left, looking through the hole for overflow, if you look carefully you can see the screw as well.
There is no need to connect the CO2 Spray Bar to the water spray bar, I currently also don't do that, but it is really important that the water under the spray bar has some flow.

Yes, I see it now. Since my Co2 bars will be shorter than my water return bars, I think it might be best to position them in the middle of each tank. Both tanks run 2 canister filters each, so I have double spray bars, one on top of the other across the backs of the tanks. I’ll try zip-tying the Co2 bar to the upper water return bar, and maybe direct some of the lower water bar flow towards it.

This is after I get them built, and then I have to sort out malfunctioning co2 regulators as well, But I will update when everything comes together!
Thanks for your help : )

 

[Yugang]

I have been testing for nearly two months a small CO2 Spray Bar for stabilising my tank at 15 ppm CO2 in overflow mode. Results so far are good, I will report more on the plants in another thread. What I hope is useful for this thread is how I optimise overflow mode, and show a real life picture to illustrate.

During the day, when CO2 is on I see probably once per minute a small bubble escaping from the cut out on the left of the CO2 Spray Bar. This guarantees that the absorption surface is constant, and hence the injection rate of CO2 into the water is constant and not dependent on regulator stability or controller. One method to verify if everything is OK is to check the size of the small gas bubble that remains after solenoid off, and remaining CO2 has been absorbed in the water. This typically takes around 20 minutes after solenoid off. The size of this remaining gas bubble is an indication of how much overflow there was during the day (purging gases that diffuse from water into the CO2 gas pocket), and that again is a measure of the stability of CO2 injection. I described the theoretical model in Horizontal CO2 Reactor - Yugang 鱼缸 Reactor

The size of the bubble is now probably around 10% of the total gas pocket when the tube is filled. This is ok, but I usually like it to be a little smaller to have even better stability. So I will give it a bit more CO2 tomorrow, this will not change CO2 injection in itself a lot (as CO2 will be overflowing), but it gives me the confidence that the stability of injection is at its very best.

 

[Yugang]

So I will give it a bit more CO2 tomorrow

A little more injection, and the size of the remaining gas bubble half an hour after solenoid off is now probably close to 5%. I could inject more but would gain little extra stability, and am happy with this.



So in summary I have three alternative indicators to check overflow mode

1. Count bps from injected CO2. For any given size of the reactor we can test the bps when it starts to overflow, and use this as the reference for the future.
2. Measure the time between bubbles escaping from the overflow, typically 1 per minute.
3. Observe the size of the remaining gas pocket after all CO2 has been dissolved.

Any of these three would do, but I prefer to have a quick check of 3, once per week or so. For non transparent plastic, the easiest is to oberserve 2 for a minute or so, and see if a bubble of gas escapes during that period.

 

[Yugang]

Take the little box that is part of the 17 piece IKEA Pruta food container set, and it will work as well. IKEA sells the full set for about 5 USD.

I am still a supporter of IKEA, but unfortunately the smallest container from their set is still a bit too large for me.

I checked out the grocery store, and took this little water bottle with a 56 mm diameter. This will give me about 2.500 mm2 reactor surface. I will mount it in the corner of my tank, mostly above the water and only the edges sticking a few mm below the surface. This be hardly visible in the tank.

The white arrow indicates the overflow that I cut out with a simple kitchen scissors.

 

[Koan]

I will mount it in the corner of my tank, mostly above the water and only the edges sticking a few mm below the surface

OK now we're getting somewhere! So we could equally use some variation on one of these



partially submerged:



to the depth which would give us appropriate diameter surface area for whatever tank size. Correct?

They even come pre-drilled with a hole for a CO2 fitting:



thus if I am understanding you correctly, giving us a "spray bar" very much in keeping with our glass Lily Pipe aesthetic

Just have to figure out the overflow. They also come in acrylic, easier to cut/drill. Or just tilt it to an angle that allows overflow escape?

Brilliant! This I could live with

Paging Aqua Rocks Colorado..
Dibs on the name

 

[Yugang]

OK now we're getting somewhere! So we could equally use some variation on one of these

View attachment 6039

partially submerged:

View attachment 6038

to the depth which would give us appropriate diameter surface area for whatever tank size. Correct?

They even come pre-drilled with a hole for a CO2 fitting:

View attachment 6040

thus if I am understanding you correctly, giving us a "spray bar" very much in keeping with our glass Lily Pipe aesthetic

Just have to figure out the overflow. They also come in acrylic, easier to cut/drill. Or just tilt it to an angle that allows overflow escape?

Brilliant! This I could live with

Paging Aqua Rocks Colorado..
Dibs on the name

If we estimate its power and assume it is a sphere with a 2.4 inch diameter, this is nearly 3000 mm2.

Important is to have sufficient water flow, and make sure the water does not stagnant.

Thinking about these beautiful glass lily pipes for small tanks, I could imagine with a small modification a version to include a full reactor function, stabilised with overflow mode. Let's hope ADA and others are listening.

EDIT: 3000 mm2 is 10% of what I use to push 1.5 pH in my tank, I corrected this.

 

[Koan]

assume it is a sphere with a 2.4 inch diameter

Well but that would be true only if the full rim was submerged on the horizontal, correct? Engaging the entire volume?



We should still be able to submerge it at an angle such that it only has a partial volume, yes? looks like approximately half or 25 gallons, less if you rotate it further?

 

[Yugang]

We should still be able to submerge it at an angle such that it only has a partial volume, yes?

That looks really interesting, tilting it to adjust the area and injection power. Just need to find a solution for the suckers to stick it on the glass.

In my initial post above I was a bit confused, a factor of 10 wrong in my calculation which I have now corrected (Partial heatstroke after hiking some mountains in HK summertime). Apologise for the error.
This size seems really good for a nano tank, or a larger tank that is targeted at lower CO2 ppm. This 3000 mm2 is roughly what I use now on my 50 gallon tank @15 ppm CO2.

 

[Yugang]

Built an even smaller CO2 Spray Bar for testing how my tank will do at ever lower injection rates. Same style as the previous one, so that I could just cut the right length of tube to obtain my target surface area.

10 cm, 1 inch tube, which gives 2.500 mm2. The ratio to 50 gallon tank surface area is now 180, this is 10% compared to the usual 17.7 that we apply for an estimated 1.5 pH drop. I estimate that with this short CO2 Spray Bar I will stabilise CO2 at about 10 ppm, to be confirmed with a drop checker.

The CO2 overflow is now drilled in the end piece, so that this end piece does not obstruct the water flow too much. On the top picture we see some waves on the meniscus of the CO2 pocket - the resulting turbulence avoids a stagnant water surface layer that would reduce the injection rate.

Adjustment of CO2 regulator is easy, just dial it down until we see a bubble escape every minute or so. With that, injection and CO2 ppm will be stable. That's all there is left from the time consuming CO2 dialling in process.

For the next weeks I will test how my tank will do with this low stabilised injection rate.

 

[Yugang]

Some insights about "dialling in CO2", while I continue to learn about CO2 Spray Bar.

When using overflow mode, be it with the reactor or with CO2 Spray Bar, we use the reactor or CO2 Spray Bar geometry to have a stable rate of injection from a CO2 gas pocket into the water. For CO2 Spray bar I now have a set of interchangeable pieces as per below, so that within minutes I can set the injection rate at a higher or lower pace, and then keep it stable.



When the CO2 Spray Bar gets a decent amount of water flow, we can use the same 17.7 ratio as used for the reactor to target a 1.5 pH drop for the tank. A 1.2 pH drop would be 50% less CO2 ppm, and this requires a 50% smaller CO2 Spray Bar (2*17.7 = 35 ratio to tank surface area). 0.9 pH drop, again 50% smaller. Dialling in is really straightforward, do the calculation and install the correct size. Verify with drop checker or pH probe.

The last couple of days I have been testing my CO2 Spray Bar with very low water flow, even virtually stagnant water. What happens here is more complex and less predictable. As we will have a stagnant water boundary layer, the transport from the CO2 gas pocket into the water will be more and more reduced by the slow diffusion of CO2 in that boundary layer, and less so on turbulent transport. As a result I did not get the full pH drop that I calculated for. The cure is relatively simple, just pick a longer CO2 Spray bar piece, check with drop checker or pH probe until target achieved.

I am posting this as I know that several members are considering to use CO2 Spray Bar on smaller tanks. When the flow is good, we can be pretty confident and have predictable results. When flow is lower, which may happen in a nano tank for example, some trial and error will be involved in dialling in at the correct injection rate.

Over time we will hopefully get more data on CO2 Spray Bar for low water flow tanks. Based in my limited experience my best guess is that low water flow (less than 1 cm/second) will give about 50% less injection that we have at higher flow, therefore I pick a Spray Bar twice the size as I would have used with a medium/high water flow.

As far as reactors are concerned, the situation is much easier as we have our water flow through the reactor and always a decent turbulent surface agitation. The injection rate is vertually independent on water flow, as long as it is not extremely slow or stagnant.

 

[*Ci*]

I finally got one of my Co2 spraybars assembled and installed. In some private correspondence with @Yugang, he determined that my “68g with a 40”x 17” surface area = 438.709 mm2 surface area. Divided by 17.7 gives 24.785 mm2 for the CO2 Spray Bar. If we would use a 1 inch diameter tube, we would need it to be 976 mm long to have that surface area.
This calculation is for about 1.5 pH drop. What we know is that 0.3 pH drop corresponds to a factor of 2 in CO2 ppm, therefore for an estimated 1.2 pH drop we could do with 976/2 = 488 length of the 1 inch tube.”

To simplify:

For a 1.5 pH drop I need a 1”x 38” (976mm) tube.
For a 1.2 pH drop I would halve that to 19” (488mm)
For a 0.9 pH drop I can halve it again to 9.5” (244mm)

My tank is med light, with low demand plants, so I do not need a high ppm of co2, so I decided to go with a 12” tube, with an extra overflow hole a little higher than halfway in case I want to dial it down some. I put a silicone plug in that hole that can be switched to the main hole if needed.



I found the clear acrylic tubes and caps on Amazon .ca and took them to a local plastics fabricator to do the cuts.

I have double spray bars on my tanks so I zip tied the Co2 bar to the top one, while the flow from the bottom one goes directly beneath the Co2 bar - it is quite turbulent across the bottom as required.




I’m glad I went with transparent pipes, as it is definitely useful to see what is going on inside. It helped with levelling and with making sure the pipe was mounted with the opening on the bottom twisted correctly so that one side is not higher than the other. Plus it looks nice and feels unobtrusive tucked up in the corner.
I just finished the installation an hour ago, so I will be tracking the pH drop over the rest of the day.

Question - my solenoid is on a time to go off for overnight and on again in the morning each day. Is there any negative to leaving it this way, or is there some reason I should let the Co2 run 24/7?

 

[FrankZ]

That looks fantastic! Great work!

I think the timer should be fine as is, it’s no different than the horizontal external reactor in what’s it’s doing. You’re is very pretty and elegant whereas, uh hum, my external is drab and ugly LOL.