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3000 Liter High Tech Planted Tank

Yes I used a PLC and had a big pH drop 1.4pH and did the drop in 30mins. If the OP wasn't aiming for such a big pH drop I cant see why it would take to long if he used the same approach as I did ie twin injection for pH drop, single injection for keeping pH/CO2 stable. The main CO2 loss will be down to the surface area of top of tank. Will need very accurate/reliable timmers as slightest error could be fatal with twin injectors and twin solenoid valves - not for faint hearted with shallow pocket's
You had fantastic technology on your tank, and I learned a lot from that (not only CO2 wise).

You will not be surprised I prefer to use the Horizontal Reactor, especially as it will be really hard to get a decent bubble reactor for 3800 litre, but I really like your double reactor with PLC approach (think you were probably the first with that).

If the OP wasn't aiming for such a big pH drop I cant see why it would take to long if he used the same approach as I did ie twin injection for pH drop, single injection for keeping pH/CO2 stable
I agree, and we all know that hobbyists have injected big tanks with bubble reactors and it worked. Aiming for 0.5 pH drop obviously will make things much easier compared to 1.5, 1000 litre will be much easier than 3800. With a partially closed system (top, or lid) easier than open top tanks with high surface agitation and outgassing.
I have indeed advised @RickyV that he may want to go for a twin reactor approach, as you did, where one reactor helps only in the morning for a fast ramp up and will then be switched off by a timer. With the Horizontal Reactor feature of 'inherent safety', as I described earlier, we could then configure the capacity of second reactor, used for steady state operation during photoperiod, to never exceed a safe maximum CO2, even in the event of a technical failure.
I have not had time to do calculations, and probably nobody on UKAPS waits for 22802 to post another incomprehensible ramble with spreadsheets, but I suspect that some of the scary CO2 consumption numbers that were reported for big tanks were at least partially due to reactor inefficiencies (bubbles not dissolving), and not essentially due to the tanks minimum requirements.

@RickyV aims for 1.0 pH drop, has a closed top system and could close it more if needed with a lid, so I am pretty confident that CO2 consumption will not necessarily be outrageous. pH/Co2 controller is a must IMO, for such configuration on very big water volume, to achieve good stability during photoperiod, while allowing for less outgassing and thus CO2 savings.

EDIT: @RickyV has a sump with more than half the surface of the tank, so if both tank and sump would be not covered this would yield a pretty big outgassing area. For this worst case, and for a 1.5 pH drop (rather than 1.0 as @RickyV objective) I calculate that a 4 inch Horizontal Reactor over the full length will do. Just to have a feel how simple even such a huge tank with sump can be solved.
 
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@RickyV journal has everything to become one of the most exciting on UKAPS.

Perhaps we move the reactor posts here to another dedicated thread, or Horizontal Reactor thread, so that we don't clutter this one with too much bubbling, plumbing and physics?
 
but I really like your double reactor with PLC approach
It did make getting a stable pH profile easier also. Plus the PLC making multiple on/off CO2 timings possible/easy (once the software was mastered. As for first hour lights was ramping up, so so had the CO2 coming on/off on in a time loop for first hour, then on all time once lights up to max. Plus when pH was reached had both off of 5mins to help reduce other shooting the pH target to allow the CO2 to be taken up in priming reactor.

I did use a pH controller at first, then wired it up to PLC so it signalled to pH was reach, this input signal was use with a bit of coding to set the ON/off timings. I even programmed it so the PLC gave me the time it took to reach the pH target. Once the trimmings became constant, I just set the time in PLC.
 
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22802 has been helping me come up a horizontal CO2 reactor design and this is the final design we ended up with. I am using 2 153cm (60 in) PVC pipe with 4 in diameter sitting next to each other (not stacked) as the reactor. I'll have a 2500 - 4000 lph pump controlling the flow either with a controller or a ball valve. The output of the reactor goes to the sump return pump. I'll be stabilizing the CO2 using lots of gas exchange from the sump overflow and surface agitation. I will use a pH controller as a failsafe.

22802 mentioned having 2 CO2 tanks/needle valves may make it a little difficult to dial in the CO2. I am thinking if I will continue with the 2 tanks approach. The idea behind using two tanks was that it was easier to work with two 20lb tanks as opposed to a 50lb tank. I am considering using only one tank for the reactor and having the second tank inject into a diffuser in the tank before the lights are on just to bring help reach the peak CO2 faster similar to how @Zeus. does it. Except that I will use one reactor and a CO2 diffuser. The reactor would maintain the CO2 for the day. My thinking was to cover the plants in CO2 bubbles for the day since I've noticed they will stick to the the plants for a good portion of the day. This was just a thought, I may stick with what I have in the diagram.
 
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Is it possible to have one hori-reactor instead off two? Will cut cost of plumbing and both will have a CO2 bubble at all times.
I would have the inlet to reactor coming from sump, as the water will be filtered, then the outlet from reactor going to tank.
If two needed I would have a small pipe so CO2 bubble in both reactors can balance, both reactors would need to be at same level. Tubing would also allow you to bleed the reactors- bleeding not really needed as air disappears in a few hours.
I would use twin solenoids with one for pH drop only and others for pH drop and maintaining steady pH. I had the neddle valve fully open on pH drop feed.
The pH controller on the pH drop line at first find the time it takes then move controller to maintaining pH stable. But you will need a very reliable timmer, which will be hard/costly. ( PLC FTW)
 
Is it possible to have one hori-reactor instead off two?
The alternative design was just one long 244 cm PVC pipe, it will probably fit but I liked the compactness of splitting the reactor in half.
I would have the inlet to reactor coming from sump, as the water will be filtered, then the outlet from reactor going to tank.
I forgot to update this on the diagram but the reactor pump will be in the sump so it will be filtered water. The thinking I had for the outlet going to the sump return pump was that it would distribute the CO2 in the tank really well since the pump is so powerful.
I would use twin solenoids with one for pH drop only and others for pH drop and maintaining steady pH. I had the neddle valve fully open on pH drop feed.
The pH controller on the pH drop line at first find the time it takes then move controller to maintaining pH stable.
Ah I understand better what you did now. So to clarify I will have one tank with the needle valve fully open (this will be connected to a CO2 diffuser in the tank), and the purpose of this CO2 line is to decrease the time it takes to reach my pH drop (and in my setup to coat the plants in CO2 bubbles). The second CO2 line going into the reactor will be used for the pH drop and for maintaining steady pH. The pH controller will shut off the pH drop line when we reach the pH drop. And then I will switch to using a timer to shut off the pH drop line after figuring out the time it takes. Then I will have to dial in the needle valve on the main CO2 line to something that will maintain steady pH, using the pH controller as a failsafe (shut off CO2 after it gets above certain drop, ideally not using the controller and maintaining steady pH without it).

I like this idea, however it does make me nervous having a line with the needle valve all the way open lol. I see why I would need a very reliable timer. This method does intimidate me a little as it seems a bit more complex than just using one CO2 line. Maybe I'm overthinking it.
 
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Is it possible to have one hori-reactor instead off two? Will cut cost of plumbing and both will have a CO2 bubble at all times.
@RickyV had some space limitations, so he decided to use the multi stage that I described here CO2 will be injected in the lower reactor, that will then start to release CO2 bubbles into the second reactor. Together they will act as one reactor, but can be build in a shorter space. The change that @RickyV made is that both reactors will sit besides each other, not on top, which makes me a little nervous but probably works well.

I would use twin solenoids with one for pH drop only and others for pH drop and maintaining steady pH.
This is still a very valuable idea. Have one solenoid switching one reactor, the other the second reactor only during ramp up. I think it makes sense if @RickyV current ideas are tested in a water-only tank, then decide if any fine tuning is necessary. The project with 3500 litre is still huge, so there may still be some surprises.
 
After some thinking I am probably going to stick with the CO2 design in the diagram just to keep things simpler. I will use Zeus method if I feel it is taking an unreasonable amount of time to reach the pH drop or once I fine tune the current design and feel comfortable with it.
 
After some thinking I am probably going to stick with the CO2 design in the diagram just to keep things simpler. I will use Zeus method if I feel it is taking an unreasonable amount of time to reach the pH drop or once I fine tune the current design and feel comfortable with it.
Makes perfect sense in my opinion as well. Start with the big steps to get first decent results, you are the first with this size of tank high tech, from there if you like some smaller steps as fine tuning. I also have some ideas, but that’s better for later and I try to not confuse the big picture right now.
 
Another idea I had penciled in was to put my next reactor in the cellar below the tank. This was to get everything CO2 wise in room below. This would have several advantages IMO, from less gear under/near tank, noise removal and a slightly increase working pressure in the CO2 reactor.
Just an idea ATM
 
I would have the inlet to reactor coming from sump, as the water will be filtered, then the outlet from reactor going to tank
Assuming that the sump is underneath the tank, this sounds like it could cause issues with the tank draining into the sump when the reactor pump is off. It feels safer to have both the inlet and the outlet at the sump.
 
Assuming that the sump is underneath the tank, this sounds like it could cause issues with the tank draining into the sump when the reactor pump is off. It feels safer to have both the inlet and the outlet at the sump.
Any output from a sump under a tank has same issue. Which has to be accounted for in size of sump, postion of outlet in tank above water level or fitting a non return valve.
Thats one of the advantages of sealed sumps ie canister filters, non backflow to worry about
 
Today I found out the source water for this tank is RO and here are the water parameters after testing; pH: 6.3 (with API drops) KH: 0 GH:0 NO3: 0.4 PO4 : 0.12 NO2: 0.002 NH3: 0.00
The return outlets to the tank also have a little bypass I can use to connect to the reactor inlet. The only potential problem I see with this is that the the reactor outlet would be going back into this return line, but I don't think it should be a problem since most of the water will still be getting returned to the tank. Here is what I am talking about:
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I also updated the CO2 reactor diagram to have a U PVC pipe connecting the 2 reactors so its essentially one long curved reactor. One problem we have though is a a big acrylic center brace.
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The brace is 51 cm in width and 2.5 cm thick in the center and 5 cm thick in those outer parts you can see in the picture. I will need to figure out how to arrange the lighting with this big brace in the middle. I was planning on using 6 rgb vivids II with 2 in the middle, but the thick acrylic may block a significant portion of the light.

I am also trying to figure out how to make the CO2 system as safe as possible. This facility has had some bad experiences running CO2 so I want to give them some peace of mind. The one failsafe I already have was using the pH controller to shut off the solenoids after pH raises above a certain threshold. I will rely on heavy gas exchange to keep the CO2 stable without the pH controller, only using the controller as a failsafe. Another idea I have is putting a big air stone on a timer to come on as soon as the lights turn off and come off as soon as the CO2 comes on.
 

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his facility has had some bad experiences running CO2 so I want to give them some peace of mind.
We can limit the power of the Horizontal Reactor so that it can never exceed 1.5 pH drop, and is inherently safe.

When you know that you can comfortably hit 1.0 pH drop, you test what happens if you inject way too much CO2, simulating a situation that something went wrong with your regulator or perhaps controller. If the tank then exceeds the 1.5 pH drop, then you adjust the reactor a bit so that it starts purging CO2 bubbles in that situation. This can be done by reducing the length of the reactor, or even easier by raising the end of the reactor a bit from its level position so that the CO2 pocket touches the water exit tube and lets bubbles escape. This slightly off-level reactor gives you then a reduced power and the safety that you want.
 
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This can be done by reducing the length of the reactor, or even easier by raising the end of the reactor a bit from its level position so that the CO2 pocket touches the water exit tube and lets bubbles escape. This slightly off-level reactor gives you then a reduced power and the safety that you want.
Oh this is great! When I build it I'll try and experiment with this off leveling to let bubbles out.

On second thought I may stick with using a pump for the CO2 reactor since I can connect the pump to a timer to turn on and off at the same time as the CO2 solenoids. Maybe connect to the pH controller? But I am thinking putting the pump on a separate timer in the event that a regulator or CO2 timer fails, the reactor pump would be off so it wouldn't matter.
 
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On second thought I may stick with using a pump for the CO2 reactor since I can connect the pump to a timer to turn on and off at the same time as the CO2 solenoids. Maybe connect to the pH controller? But I am thinking putting the pump on a separate timer in the event that a regulator or CO2 timer fails, the reactor pump would be off so it wouldn't matter.
I think there are several ways to make it work, and part of it is your personal risk assessment and preference. I can give my own opinion, but do not want to clutter your journal too much and we may follow up in detail in PM's.

I would consider the first step a 'prototype' optimisation, as your tank is so much bigger than other tanks and you first want to get the basics right. I would adjust the length of the reactor so that in the worst case it does not more than 1.5 pH drop. In well oxygenated water fish are unlikely so suffer from this. When you have your 'prototype reactor' right-sized, you can consider that job done and glue all parts definitively together.

Now there are two ways to use a pH controller. One is to use it as a 'safety net', turning off solenoids if pH drops more than a safe level. As you have already built in this safety in your reactor, as per above, you could argue that you don't need that service from a pH controller. The second way to use it, my personal preference, is to use the pH controller to allow the CO2 to ramp up fast, using the reactors full 1.5 pH capacity and then stabilise at 1.0 pH drop during photoperiod. I know that your preference is to stabilise with surface agitation, but my personal view (and not necessarily the best opinion, and it is your call what you like best) is that covered with a lid that influences outgassing, and especially for such big tank, it is easier done with the pH/CO2 controller.

I know that you can buy CO2 at a low price, don't care too much about consumption. I really like @Zeus. dual reactor approach, but that serves mainly the purpose of a fast ramp up and then stabilisation on just one reactor. You may not need this, if you don't care too much about a longer ramp up time (could be some hours for your big tank when fully degassed), and the additional CO2 consumption from that.

Let me not make this posting even longer -- I'll add by PM, ok?
 
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The second way to use it, my personal preference, is to use the pH controller to allow the CO2 to ramp up fast, using the reactors full 1.5 pH capacity and then stabilise at 1.0 pH drop during photoperiod. I know that your preference is to stabilise with surface agitation, but my personal view (and not necessarily the best opinion, and it is your call what you like best) is that covered with a lid that influences outgassing, and especially for such big tank, it is easier done with the pH/CO2 controller.
I've been sleeping on this, and am not anymore 100% sure that using the pH/CO2 controller for stabilising CO2 on your tank is my preference. The argument is rather technical, but the conclusion is that I would recommend to try, and see the results on the tank and then decide what method works best for your tank.

When using a pH/CO2 controller to stabilise my 250 liter tank with CO2 Spray Bar (same principle of course) it worked extremely well. Stability within a couple of hundredths pH, much below the 0.1 pH stability which is of rule of thumb in the hobby. The issue however, and I did not think deeply enough about that, is that your tank is 15 times bigger, and your reactor 11 times bigger than mine, and that is relevant for what happens with the control mechanism.

I believe it won't help on this forum to go too deep in the technicalities of control systems (I'm also not a specialist), trying to understand what will be the quality of CO2 stability when using a pH/CO2 controller on a Horizontal Reactor in your tank. When the controller says 'OFF', i.e solenoid off, there is still a CO2 pocket of gas in the reactor (irrespective of bubble reactor or horizontal reactor) that may give some 'overshoot'. Then, when the controller says "ON", the reactor for such a big tank will need some time to get to its full power. This all is to illustrate that what happens in the tank with CO2 ppm is the consequence of a chain of events after the controller decides to do something. Making an accurate prediction how well the controller will work on your setup is a project in itself, and without calculations not easy to estimate. The most pragmatic is to test, and decide based on test result imo.
 
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When the controller says 'OFF', i.e solenoid off, there is still a CO2 pocket of gas in the reactor (irrespective of bubble reactor or horizontal reactor) that may give some 'overshoot'. Then, when the controller says "ON", the reactor for such a big tank will need some time to get to its full power. This all is to illustrate that what happens in the tank with CO2 ppm is the consequence of a chain of events after the controller decides to do something.
These are some interesting thoughts, it is indeed a challenge to figure this out. Another reason I preferred to not rely on a controller is because I feel it is another piece of equipment that can fail. I think some of the accidents that have happened in this facility was due to controllers failing. I'll be researching to find a reliable/precise controller. Will also make sure to do regular maintenance of the pH probe. But I also feel that stabilizing the pH using gas exchange is safer since I will have so much more oxygen in the tank making the fish tolerate elevated CO2 levels. Another thing is that if somehow a timer failed and a solenoid turned on at the wrong time or never turned off, the CO2 will not go much higher than the equilibrium point. And I would also have the giant airstone on during hours that CO2 is supposed off. But as you said I will need to experiment and figure out what works since things can work very differently on such a big tank.
 
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If you have a lid on the tank then you can (in theory) get a controller to ensure the CO2 concentration in the headspace above the water is maintained at 2% and your water will equilibrate to around 25 PPM CO2. We used to have tissue culture incubators that worked this way: you set them to maintain an atmosphere of 5% CO2 and with the phosphate buffered system in the tissue culture media you ensured a nicely stable pH. You could dial the CO2 percentage up or down to whatever you liked and we had them hooked up to 50 pound CO2 cylinders. I don't know how long it would take to equilibrate the water in your aquarium, maybe a couple days if you have good water movement, and then you don't have to worry about it after that. These systems were really reliable.
 
If you have a lid on the tank then you can (in theory) get a controller to ensure the CO2 concentration in the headspace above the water is maintained at 2% and your water will equilibrate to around 25 PPM CO2. We used to have tissue culture incubators that worked this way: you set them to maintain an atmosphere of 5% CO2 and with the phosphate buffered system in the tissue culture media you ensured a nicely stable pH. You could dial the CO2 percentage up or down to whatever you liked and we had them hooked up to 50 pound CO2 cylinders. I don't know how long it would take to equilibrate the water in your aquarium, maybe a couple days if you have good water movement, and then you don't have to worry about it after that. These systems were really reliable.
Wow this is a really interesting method for injecting CO2. I'm guessing I would also have to cover the sump and that headspsce above it would equilibrate that same as the display tank. Wouldn't this method require me to open the lid as little as possible? Or perhaps the volume of the tank is so large it wouldn't make a significant difference in CO2 concentration if I opened the lid for feeds/maintenance.
 
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