Pressurized CO2 System

[theotheragentm]

Okay, I've decided to look into a pressurized CO2 system. I am pretty sure I can get the pieces cheaper through my work. We do process applications for industrial and commercial companies.

1. CO2 tank.
2. Pressure regulator w/ upstream and downstream gauges.
3. Check Valve
4. Needle Valve
5. Solenoid Valve
6. pH Meter
7. Air tubing

The one piece I don't know if I can get any cheaper is the piece that will disperse the gas into the tank itself. What should I use?

From what I can tell, CO2 comes out of the tank, regulates down, passes through the solenoid when it's on (based on receiving power and not meeting pH in the tank), and then it's dispersed into the tank. What is the needle valve used for?

Thanks in advance for any help. If I get these parts cheaper, I'll see if I can help out people on these forums too with their own setups.

[neilanh]

The needle valve gives you finer control of the flow rate of the CO2 gas. Think of it as another low-side regulator, essentially. The addition of a bubble counter on the output of the needle valve is a way to guage how much flow you're getting.

As for diffusion, there's a ton of different methods that can be deployed. Usually, a tanks filtration method will help to dictate the best means for diffusion of the gas into the water column. One can go with an inline reactor if using a canister filter or a closed loop system, or a micro- diffusing airstone or "glass diffuser" can also be used. Others use a venturi system to blow the bubbles around the tank.

[theotheragentm]

I have a cannister. How do you diffuse it into the system when you have a cannister?

Where are you placing the needle valve in relation to the other pieces of equipment? What pressure are you looking for with the CO2 when you're dispersing it?

[neilanh]

Check out this link by Sparky on how to build an inline reactor

This picture shows the setup really well


The needle valve is the brass knob on the right directly connected to the bubble counter.

On my system, I run the regulator at a low side pressure of 30psi, then use the needle valve to adjust to the desired flow rate (measured in bubbles per second, or bps). Depending on tank size, method of diffusion, amount of surface turbulence, etc, will determine your bubble rate.

[JustOneMore20]

If its a larger tank (I think you have a 55g, right?) then I suggest using an inline reactor or a powerhead. The inline external reactor would get it out of the tank, so might be worth looking into.

Also, you don't have to get a pH monitor/meter unless you just want to......its a luxury item and not a necessity.

[warped1]

You guys don't mess around - I'm talking big leagues here
I never new so much could be involved with a tank
I'll be happy just to get my 36gal running with fake plants and drift wood - I could only hope that I - one day - have this kind of dedication and knowledge

[neilanh]

It seems like a lot, doesn't it warped? It's not that bad really.

[theotheragentm]

Let's see if I got this right. With that image you have there, the tank would be hooked up on the left side of the PRV. Then you're traveling through the solenoid and then upward into the bubble counter. Is that right?

What do these external reactors look like?

As far as the pH meter goes, I am pretty sure I can get my hands on them pretty cheaply, and it does add a bit of control.

[neilanh]

That's correct. The left guage is the high side, or tank pressure. Right guage is the low side controlled pressure. Through the solenoid (part with the cord), then through the needle valve and into the bubble counter.

In the link above, here's a shot from that DIY guide, showing what an external inline reactor can look like.


Nothing wrong with running a pH controller at all, it adds a bit of safety and takes away a lot of the need for tuning/tweaking the system, but adds the complexity of needing to maintain the probe and calibrations of the controller. Not a big deal on either route, just different techniques.

[theotheragentm]

How does the bubble counter work exactly? I assume it's filled with water, otherwise it would be impossible to count bubbles. I calculate the bubbles needed per second, and I just throttle down the needle valve until I reach that point? What constitutes a bubble? Is there a size?



This is the Drs. Foster & Smith ultimate setup, according to them. It looks so horribly cluttered, but let me see if I get this right. CO2 out of the bottle, through the regulator, past the solenoid when it's energized, through a needle valve, into a bubble counter, into a reactor (for dissolving into water), and into the tank. The pH meter feeds back to the controller, which tells when the CO2 level is saturated and cuts signal to the solenoid.

Instead of the reactor, could I just use something like this? Would this give me a fine enough mist of bubbles that I could place it under a small powerhead and have the powerhead further disperse it into the water?

[neilanh]

You pretty much nailed it with your explanation. The bubble counter is just an indicator of the flow rate to help you adjust the rate. You will determine how much you need based on your CO2 calculations of what's in the water column and adjust accordingly.

The link you provided is to a glass diffuser. These work pretty well too, but not as efficient as an inline reactor.

[An t-iasg]

At one point I had a limewood airstone as my diffuser. I placed it under a Mini-Jet water pump so that all the CO2 bubbles leaving the airstone got pulled into the pump. The pump then disbursed them all over the tank. This is called the "mist" diffusion method. This method works very well also and it's similar to the inline reactor in that the CO2 is broken down into smaller bubbles too. You could use that glass diffuser you linked with this method. I used glass diffusers with the ceramic airstone too. After a while the ceramic gets clogged (in my case it was 8 months). I soaked it in a dilute bleach solution but that didn't work after awhile either, so I switched to the limewood airstones. They lasted about 3 months. I rotated them and let them dry out periodically, and they were cheap enough to replace after 3 months. I wouldn't want to replace the glass airstone every 8 months or so.

The mist method can work very well, but its possible limitation is the type of airstone you have - ceramic and wood both have good and bad points. The inline reactor method takes some building up front but it doesn't have the limitations of the airstones.

[theotheragentm]

The reactor just seems a bit large for my tastes, whether it's outside of the tank or not.

[pitt420dude]

Warped1, this stuff confused me too at first, but with time and a lot of reading it can be digested.

IMO, once you get your tank, regulator, solenoid and bubble counter straightened out, the toughest part (for me at least) was getting 100% diffusion. This week I'm going to plug a DIY reactor (pvc w/ bioballs) into the downflow of my cannister filter. The rising action of the bubble fights the falling action of the water and aids diffusion. If any bubbles actually make it into the cannister (fluval 304), they get choped up to the impellor and (I hope) completley dissolved into the water column by the time the flow hits the output nozzle.

IN THEORY!

A bigger tank w/ more surface agitation means more bubbles. Every reactor has a "max diffusion capacity": the best reactor in the world isn't going to be able to diffuse 100 bps, wheras even a somewhat crappily built reactor should be able to diffuse 1 bps or less.

[theotheragentm]

So while 100% isn't really obtainable, what's your opinion on the best method based on ease of use? CO2 is relatively cheap, so if I "waste" some with less the perfect diffusion, I'm not too worried.

[Purrbox]

The best method as far as plant growth currently seems to be the mist method. A lot of people don't like having a fine mist of bubbles in their aquarium though, so it's not for everyone.

The next runner up would be either the inline reactor or intank reactor. I know that you don't like the size of the inline reactor, BUT keep in mind that the picture from DrsFosterSmith has that setup on a much smaller aquarium than it would probably ever be run on. That particular reactor is rated for upto a 500 gallon aquarium and the aquarium pictured is probably only 20-25 gallons. The reactor is only 15" long and 3" in diameter. An appropriately sized inline reactor for an aquarium will be easily hid behind the aquarium or under the stand.

[Tankrupt]

heres a nice easy calculator for c02/ph levels, c02 as a carbon source is fairly easy to manage, I always had trouble with the other ferts needed and balancing growth versus pruning

Measuring CO2 levels in a Planted Tank