# CO2: Semi-automatic or Automatic



## AndreyT (Apr 28, 2011)

Automatic CO2 system is a feedback-based system, that is equipped with a pH sensor in the tank. The sensor continuously monitors the pH levels and the feedback circuitry continuously adjusts the CO2 flow to keep the pH at a preset value. Automatic systems can perform either gradual adjustment of CO2 flow, or use a discrete on-off valve. Such systems are also called "computer-controlled". They are often implemented as an integral part of a more extensive computer-based system that monitors and automatically controls many different water parameters. Although there are also standalone dedicated systems that control CO2 injection only.

As for semi-automatic system... I'd guess that this is a system that can turn itself on and off on a schedule, but has no feedback-based self-control. I.e. it is controlled by a solenoid with a timer.

The advantages of automatic system should be rather obvious. It basically guarantees that the appropriate amounts of CO2 are injected at all times without any user intervention (i.e. automatically, as the name suggests). Of course, such systems are typically much more expensive, in terms of both initial investment and routine maintenance (the sensors require periodic replacement).


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## kevmo911 (Sep 24, 2010)

Regardless of semantics, if the OP could elaborate a bit, we could probably give better feedback.


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## AndreyT (Apr 28, 2011)

An example of a _semi-automatic_ system can be seen here 

http://www.drsfostersmith.com/1/2/7271-how-set-a-semi-automatic-co2-injection-system.html

An example of a basic _automatic_ system can be seen here

http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3747+9933&pcatid=9933

In the end, it all, of course, boils down to what the original poster wanted to ask.


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## AlecFish (Nov 26, 2011)

Have any of you used either a semi or automatic co2 system? 
As a teenager, I'm sort of on a budget but I'm willing to spend a decent amount. I found this one on aquabuys its a fully-automatic co2 system
- http://www.aquabuys.com/p/co2-combo-regulator-ph-controller.html
Its $198 so its a big investment for me at least. 

I really like the simplicity of the automatic systems. It seems like the semi-auto systems are a bit unsafe and don't have the monitoring that I need. 

I have a couple questions...

What does the solenoid do? 

What are the uses of the drop checker? 

Thanks


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## AndreyT (Apr 28, 2011)

"Solenoid" actually stands for _solenoid valve_. It is just a valve that can open or close the flow of gas. It is an on-off valve, it has no intermediate positions: the flow of gas is either fully open or fully closed. 

The valve is externally controlled by electrical current (this is when the "solenoid" fits in). When you supply the current, the valve opens. Otherwise it stays closed. In case of the system you linked it is just the ordinary 110V AC from the electrical outlet. So, the pressure regulator will have an ordinary cable sticking out of it with an ordinary AC plug. 

So, the question is how and when you are going to supply the current to open the valve. You can simply plug the solenoid directly into a 110V AC outlet. That way it will stay open at all times (or until you unplug it). That would be a "manual" system. You can also plug the solenoid into an ordinary household timer programmed to open the valve during the day and close at night, ending up with a "semi-automatic" system. Or you can plug in into a pH controller, which will decide when to open it and when to close it by measuring the current pH level of the water in the tank. That would be the "automatic" system. pH controller performs its measurements using a connected sensor that you'll have to install in the tank.

Drop checker is just a method of manual pH measuring. It is a good idea to have one in your tank as a backup way to measure the current pH levels, i.e. to see that the automatic system is working properly.

P.S. Note that solenoid valves make a pretty audible click when they open and close (mine does at least, could depend on the valve).. In a semi-automatic system it clicks only twice a day: in the morning and in the evening. With automatic system it will click much more often. I can imagine some people might not like it. It also puts extra wear on the solenoid. Well, the point is I'm not sure the fully automatic system is really worth it. Virtually everybody uses an ordinary timer on their solenoids and a manual pH checker. It all works perfectly fine. If I were you, I'd spend the money on quality pressure regulator-solenoid valve combination, instead of buying a low-end automatic system.


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## Daximus (Oct 19, 2011)

Aquarist14 said:


> Have any of you used either a semi or automatic co2 system?
> 
> ....
> 
> ...


Don't be scared of a "semi-automatic" system, they are perfectly safe. Anything can break mind you, so nothing is perfect...but an automatic system can break just as easily. I wouldn't call an automatic system "easier" by any means...they still require setup and work to get them calibrated. I haven't touched my semi-automatic system in months. I'm not trying to steer you away from an automatic system...they are very cool. I'm just quelling the fear of semi-automatic systems. Don't properly both can be very safe...as safe as anything injecting a compressed gas into a tank full of living creatures anyways, lol. As with anything you can make is as complex as it need by. I simply think of it as a controlled gas leak on a timer. :icon_cool

A drop checker checks the level of Co2 in a given aquarium by use of a special solution. I personally don't use one...but they are a very good thing to have. 

A solenoid is simply an electronic switch. We like them because we can plug them into timers like our lights. 

Here is my entire system (minus the diffuser). 

http://www.amazon.com/AQUATEK-Regulator-COOL-TOUCH-SOLENOID/dp/B0041YLM7G/ref=pd_sim_sg_2

http://www.amazon.com/5-LB-CO2-Cylinder-Aluminum/dp/B0023VE8F2/ref=pd_sim_petsupplies_3


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## talontsiawd (Oct 19, 2008)

I haven't used an "automatic" system myself. Most people use a "semi automatic" system however. If you are using quality components, I see absolutely no reason to invest extra money in a PH controller. Also, you don't need to buy everything together, you can buy the PH controller later down the road if you want to incorporate it later.


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