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Discussion Starter #1
This is a less confusing repeat of the question I asked in the equipment section ...'Free DIY CO2 regulator'. Sorry it wasn't meant to be click bait, people only read the FREE bit I think and I didn't get any replies apart from "where the free regulator" :(

I always thought it was impossible (or perhaps just reckless) to turn a yeast CO2 system off at night because they can explode, but I woke up to gasping fish a few weeks ago and I suspect the CO2 level has risen too high by morning so leaving them on 24/7 is dangerous as well.
I have seen a post on another forum where a guy has proposed a DIY pressure regulator that stores the excess CO2 and so it can be turned off and it also solves the problem of uneven CO2 production rates.
It seems like a good idea but I would like to know if anyone here has ever seen a system like it or better still tried it ..... its very nearly free :)
Please can you have a look at :
Pressure Regulating A DIY CO2 System | Think Fish Tropical Aquarium Forum
and let me know what you think.
 

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I carbonate beverages using 6 2 liter bottles. One holds the yeast sugar mix and 5 are for holding excess CO2. To turn off the system use a surgical tubing clamp or two. Not sure it will fit airline tubing? I been thinking of adapting this for use in the aquarium. But with a cheapish Hoke 3132M2B needle valve I got, may be able to adapt after the tubing clamps. So I could leave the needle valve set at a particular level and turn on off with the tubing clamps. But I would suspect there would be a burst of CO2 when first turned on if the needle valve is not so good.

May not work well but there is an idea for those of us with low funds. Not planning to do this but I have the stuff if I get the time. My CO2 is really low considering my PH and temperature and struggle growing plants but I really like my fish and dont want them stressed. So I have some reservations. And Excel ends up killing some of my plants and sometimes fish no matter how little I use. Thats my 2 cents.
 

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Discussion Starter #3
So it sound like you use the buffer tank solution that is shown as the partial solution.
http://www.thinkfish.co.uk/forums/index.php?action=dlattach;topic=2442.0;attach=3360;image
You just have more volume than the calculated example.
I still really like the look of the regulated version, I see he added a follow up how-to post showing a bit of the build. If anything the regulated version looks easier than the buffer tank because the pressure seals don't have to be so strong.
 

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Why not just add an airstone on a timer to counter the CO2 at night? CO2 an O2 are not mutually exclusive...
 

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Discussion Starter #5
I already have an air stone running during the day and I set the CO2 to give the levels I need. Now of course if I switched the air pump at night it would be worse but the plants will still stop absorbing CO2 a night, do I need to add another air pump? The pressurised guys stop the CO2 at night and it only the explosion risk that normally stops a Yeast system doing the same. The regulator seems to do this so will probably give it a go, it doesn't look like more than 30 minutes of work if I shut it down manually at night.
 

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I got mine kind of balanced to where it does not hit extremes, the airstone runs lightly all day (inside a breeding net) and I never switch off the CO2.

In your system, the airstone will cycle CO2 rich water to the surface where it will try to find equilibrium with the atmosphere (off gas), so the CO2 would be reduced and oxygen would be increased (when it is low).


Manual, is the snake's name, and he will bite you sooner or later.
 

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Discussion Starter #7
Thanks Nordic, I accept your points 100% but that was the reason for the post, I'm trying to improve on it. I wondered if the regulator in the other forum was a solution Did you have a look at the link in the first post, the first two pages discuss the problem and then 3 and 4 give a solution?
 

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I did, honestly, my experience is that every connector is another potential leak. I keep it nice and simple.
Scale up the gas supply bottle till it meets your needs, set and forget (every interaction is an opportunity for error).
You generally don't need (want) too much surface agitation in the light period. Your plants will be oversaturating your water with O2, to a higher level than without CO2.
It is only during the dark period that you need increased gas exchange with the atmosphere.
 

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Discussion Starter #9
Yes you are right about the connections and leaks. I used a cheap plastic throttle valve for a while until I realised it was leaking as much CO2 as the tank was getting Doh! I once thought about trying to measure if the system was pressure tight by doing a pressure drop test (with a small volume of gas its possible to measure truly tiny leaks) but then I remembered I had a life.
Well I tried the regulator and it seems to work, it was a bit more than a half hour work because I didn't want to loose my CO2 pressures so I faffed around clamping pipes and venting air from bottles before reconnecting it. It only added one extra connection to the two generator plus buffer tank system I had. This is because the buffer is still there, just with an additional tube in the cap and it uses a continuous run of tube all the way from inside the buffer to inside the header tank. Cool.
The header tank is on a high shelf hidden in a large vase and now contains about 3cm of water and the reactor has a steady stream of bubbles. Initially I put it on top of the tank but the CO2 went into the header tank rather than the reactor so I raised 60cm and the increased head of water started the reactor flow back up. When I clamped the tube going to the tank I could measure the water level rise over a few hours. Opening the clamp the bubbles just started up again after about 10 minutes, I guess some water had entered the reactor and had to be purged.
In principle I would say the theory works and its got potential, I will have a look for a valve to automate it and see how it performs linked to the lights.
 

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Sometimes at the beginning it is possible to set up a siphon with the tube and backfill your yeast bottles... don't ask how I know.
 

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I always thought it was impossible (or perhaps just reckless) to turn a yeast CO2 system off at night because they can explode, but I woke up to gasping fish a few weeks ago and I suspect the CO2 level has risen too high by morning so leaving them on 24/7 is dangerous as well.
Switch to a DIY Citric Acid/Baking Soda System. I personally run it 24/7 but with the way the setup is, you can easily shut it off and it will be in equilibrium between the 2 bottles and pressure will not continue to rise. You could hook it up to a timer and have it turn on when your lights turn on as well if you want to go that route but it will be more expensive for sure with the solenoid.

How to set it up

Check out the pictures of my setup here:

http://www.plantedtank.net/forums/20-diy/1032785-forced-pressure-co2-generator.html#post9204585
 

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This is what I'm running and you can turn it off at night, the excess CO2 fills the last bottle in line to be pumped into the tank when you turn it on the next morning.
 

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This is what I'm running and you can turn it off at night, the excess CO2 fills the last bottle in line to be pumped into the tank when you turn it on the next morning.
Yes but what if you're away on vacation? You're going to either risk having the bottle explode or starve your plants.

In the citric acid/baking soda setup, once the CO2 is generated, it creates an equilibrium of pressure with both bottles which then stops any new CO2 generation. Basically, no citric acid/water solution will flow from Bottle A to Bottle B at that point in time and won't create more CO2. When CO2 is used (via going out the diffuser), more citric acid solution will automatically go into Bottle B to create more CO2 thus creating the equilibrium again. It always wants to create that equilibrium between the 2 bottles. When there is equilibrium, it is stable and no pressure will increase. However, I will say that it isn't perfect in that respect as I have seen the pressure increase slightly on the pressure gauge above what I set it to but it is not that much higher and all within tolerance of the 2L bottle.

It really is an ingenious setup that works well. For me, it's just about getting it to last longer which I think I can with additional bottles and using T connectors to tap them in together.
 

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Not a worry, there is a pressure release valve on the liquid/water separator. Vacation, I'll have to employ some electrical switches.
 

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Discussion Starter #16
MCSLABS,
Yes you are running a basic buffer tank setup and that is what I was using before this test. Check out the pressure calculation in the on page two of the link in the first post, a buffer is an improvement on no buffer but I would not trust it enough to switch it off at night, pressure relief or not.
I'm not too sure why the pump is needed for the CO2 but if it is then a peristaltic pump is what you should be using there is no chance of any leaks in these and when they are stopped they act as a valve as well.
I'm unclear how combining the air and CO2 systems helps, is it just to have a single air stone?
Opening valve 3 would presumable vent a lot of your CO2 pressure out rather than admit air as valve 3 opens then once the pressure is lost you would dilute your CO2 with air, what is the advantage in that?
BTW this was hopefully constructive criticism/understanding the thinking rather than negativity :)

Thanks No92,
I have seen references to the citric acid/baking soda before but thought it just referred to a different 'fuel' for the system, I didn't look at you links yet but that where I'm going now.

Thanks Guys
 

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Discussion Starter #17
MCSLABS,
Yes you are running a basic buffer tank setup and that is what I was using before this test. Check out the pressure calculation in the on page two of the link in the first post, a buffer is an improvement on no buffer but I would not trust it enough to switch it off at night, pressure relief or not.
I'm not too sure why the pump is needed for the CO2 but if it is then a peristaltic pump is what you should be using there is no chance of any leaks in these and when they are stopped they act as a valve as well.
I'm unclear how combining the air and CO2 systems helps, is it just to have a single air stone?
Opening valve 3 would presumable vent a lot of your CO2 pressure out rather than admit air as valve 3 opens then once the pressure is lost you would dilute your CO2 with air, what is the advantage in that?
BTW this was hopefully constructive criticism/understanding the thinking rather than negativity :)

Thanks No92,
I have seen references to the citric acid/baking soda before but thought it just referred to a different 'fuel' for the system, I didn't look at you links yet but that where I'm going now.

Thanks Guys
 

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Discussion Starter #18
Okay No92 I'm back.
I watched your very fine video then found the setup instruction that explained the principle. A cunning ruse and I love the simplicity, and as you said eventually you get to no pressure differential therefore no flow and no more gas.
What is the system like in practice, I thought it might be a bit ticklish to obtain stability without sudden pressure differentials sucking or blowing liquids from one bottle to another and changing the rate of reaction quite considerably.
The contents of bottle A suddenly appearing in bottle B as you open the valve and the outlet pressure drops rapidly is probably quite interesting to watch :) Run lads she's gonna blowwww .... or is that just my evil imagination?
 

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It is a regular small air pump that had been sealed with silicone to have an inlet as well as an outlet. Valve 3 is opened to let room air in and travel through to the pump picking up CO2 along the way. Advantage is the CO2 is now in a pressurized stream and can be injected anywhere in the tank through a air stone. When valve 3 is closed, as in the lights off mode, CO2 is forced into the liq/gas separator bottle which has a one way check valve in line as well, so pressure is released there. If the check valve should happen to fail (highly unlikely) the result in pressure build up would blow off the lines before enough pressure built to compromise the reactor jars. The lines are silicone and pressure fitted through the lids. CO2 dissolves much more readily than that of O2.
 

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Hello All,
I just joined the forum and saw this on regulating Yeast CO2 generators only to find it is a link to my system :) I'm so pleased !

I have made this regulator a few times both for my own tanks and for friends. It certainly works on the ceramic disk/spiral glass reactors and I am about to set up an inline diffuser on the next system.
I have yet to find that it is lack of pressure in a Yeast CO2 systems that causes problems, in my experience and as the calculation suggest they get to uncomfortable pressures with the greatest of ease. A combination of low system volumes, low system flow rates and a highly variable input is the killer. My view is that it is the slow start to generation (impatience?) and the production inconsistency that causes the disappointment for most until they get the hang of it.
To combat both of these I routinely use three generators and will vary the yeast mixtures in some of the bottles depending on whether the system is primed and running or needs a boost from a single 'hot' bottle. However three generators is capable of producing a lot of CO2 and this is where the idea of the storage and regulation started.
A simple buffer tank provides storage but only by building up pressure but this in turn makes the regulation of flow to the reactor a problem, it has to be constantly adjusted to give a constant flow rate - and who wants to do that?
I had a look for a small low flow pressure regulator, but as I came from the gas industry I knew that this isn't a normal spec and the just isn't the demand for them. That's when I went back to basics and combined the two, used water head to operate it so there are no moving parts to get gooed up.

Once a system is running the water level in the header bottle tells me if the bottles are running out of steam and if one needs to be refreshed. The 2 or 3 litres of stored CO2 is easily enough to allow a new bottle to establish.
When the CO2 production overtakes demand (and it certainly will at times) all that happens is the excess CO2 volume is bubbled out of the header tank, but as importantly the pressure and stored CO2 isn't lost as with the emergency release caps. CO2 is maintained just under the maximum pressure and the 2/3 litre of buffer capacity is still there.

Typically I put the header about 1-1.2metre above water surface and this seems to give a good pressure for the spiral glass rectors without a need for restrictor valves. I set the bubble rate by the raising or lowering the header bottle, and once it is set there is no need to adjust again.
In my last system the generators were under the tank but the header tank was out of sight in another room.

I have added the system description to the post so you don't have to go looking elsewhere any more, but please do look at ThinkFish forum because there is plenty more useful stuff and the natives are friendly.

So long and thanks for all the fish.
 

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