I have just gone through the learning curve (and still learning more as I go) so I know the feeling. So much stuff, so confusing, and no one ever agrees on what to get.
The best antidote to that is to understand what the parts are and what they're used for. Because even if someone gave you a link to something to buy, you will still need to set it up (even if it comes connected) and know how to operate it. There is nothing better than actually understanding it all.
So in my best layman's language, let me try to go over the parts. I know if I get something wrong, someone will be quick to correct me.
I have also decided to link each part to the pages on greenleafaquariums.com. I am not advertising for them, but using their pictures for part identification.
This is the big tank that's filled with CO2. You can get different sizes, but most get either 5 lbs or 10 lbs. Obviously, the more you get, the less often you have to refill it.
They also come in different metals. Aluminum is usually preferred because it's lighter, but steel works just fine. One thing to keep in mind with an aluminum cylinder is that some shops won't refill while you wait. They prefer to exchange cylinders which means you'd have to give them your nice aluminum cylinder in exchange for one of their heavy steel ones.
Places to buy a cylinder and get it filled. Look for welding shops and any place that sells home brew (beer) stuff.
Connected to the cylinder is a regulator. That's that part you see with the two gauges. The regulator is like the main control for the CO2. You use it to release the CO2 from the cylinder at a certain amount. One gauge will tell you how much CO2 is in your cylinder while the other gauge shows you how much you're allowing out.
It's that squarish block you see that's attached to the regulator. The solenoid basically turns the system on or off. When the solenoid is turned on, it allows the CO2 to go ahead and pass through. If it's turned off, it stops the CO2 from passing.
Next is the bubble counter. It's attached to the solenoid. It looks like a fat, short test tube with water in it. It does two things. It further fine tunes the amount of CO2 you're dosing into your tank; plus, it lets you count how many bubbles are coming out to give you some visual way of knowing if you need to let more out or not.
It's hard to figure out the difference from these three parts because they all interact together. So, briefly, to help get the hang of it, try to think of them this way.
The regulator (1) shows you how much CO2 is in the cylinder, (2) shows you how much CO2 you're letting out of the cylinder and (3) is used to adjust how much CO2 you're dosing.
The solenoid is like the start/stop of the CO2.
And the bubble counter (1) fine tunes the amount of CO2 you're dosing the tank and (2) lets you count the bubbles of CO2 you're dosing.
All three parts will probably come already connected when you buy a full setup.
Okay, from there, the CO2 is now ready to go into the tank. Now you need to decide on whether to use diffuser or reactor. Both achieve the same goal, just in different ways. The goal is to dissolve the CO2 into the water so it can be used by the plants. The better the CO2 is dissolved, the more the plants can use. The less it's dissolved, the more CO2 just bubbles up to the surface and pops into the air and is wasted.
So there are two things that can help dissolve the CO2 into the water. The longer a CO2 bubble is held underwater, the longer it has a chance to dissolve in that water. Also, if the CO2 can come out in tiny bubbles instead of big ones, it creates for surface space on the bubbles to help dissolve the CO2. Obviously, a small bubble will need less time to dissolve than a big bubble.
These are used inside the aquarium. For many DIY setups, this is the ladder that forces the CO2 bubble to go back and forth a lot before finally reaching the top. This is also the little bowls you see that have a small white disk inside. The disk has tiny holes that forces the CO2 into tiny bubbles.
A reactor is generally used outside of the aquarium, attached to the outlet of a canister filter. The idea with a reactor is to put the CO2 in contact with the water in a manner that gives it time to dissolve. Then the water with the dissolved CO2 is run through the filter's outlet.
At this point, you have gone all the way from the CO2 in the cylinder to having it dissolved in the water.
A couple of minor accessories that you should take note of:
Most normal tubing can leak CO2 so it's best to use tubing specifically for CO2. It's not expensive.
Anytime you have tubing that pushes CO2 into water, it's possible for that to get reversed so that the water comes back down the tubing. Therefore, you want to add a check valve to prevent the water from coming back down. It lets things pass only one direction, and in this case, it'll be the direction of the CO2 towards the water.
This is like a plastic o-ring or washer that helps to ensure that the CO2 coming from the cylinder to the regulator does not leak. You have to have one. Most setups come with a plastic one, but you can also get a brass one that's reusable.
This is placed inside your tank just like a thermometer. There is a liquid placed inside that will change colors to give you an indication of how much CO2 is dissolved in the water column. A blue color is low CO2, green is just right and yellow is high CO2. The double-check drop checker has two sections, one to measure the CO2 in the tank and the other is a colored liquid to show you the shade of green considered just right. It's a nice comparison rather than guessing (blue green, bright green, yellow green?).
And then last, but not least, the optional part.
You can put your entire CO2 system on a timer if you want. That way it's only turned on when the lights are on which is when plants actively grow. Many people do this.
However, CO2 and pH are related so the more CO2 you dose, the lower your pH will become. Sometimes people want to put the entire system on a pH controller that will then automatically dose the CO2 in order to maintain a specific pH setting that you set.
I have one. The advantage is that my CO2 levels are definitely good when the lights come on. No more swings of low CO2 in the morning that falls off again each night. But a timer could be set up to do the same thing.
I also like having a more stable pH. A timer cannot do that.
A drawback is not only the price, but you have to maintain the calibration and keep the probe clean. It's not something you stick in your tank, allow algae to grow all over it, and forget about it (like most of our in-tank equipment
). You will need to take a little time about once a month to be sure it's clean, calibrated and working properly. If it isn't, it could malfunction and dose too much CO2 into your tank with disastrous results. Of course, if you set up your CO2 regulator and bubble counter so that even if CO2 was dosed at full amounts all night long, it still won't be an overdose because you've set the maximum amount coming out of the cylinder to a safe level.
I'm sure that's all pretty rambled. I hope it helps. I sometimes believe it's much more helpful to have things explained from one layman (or woman) to another when first starting off. After you get your setup going, it'll all seem pretty simple. It's a lot of parts, but they're all easy to understand.
Here are some helpful links. One shows you how to connect it all. The other shows you how to build a nice, inexpensive reactor, and the last one shows you how to install a pH controller (my thread begging for help when I installed mine!).
I hope that helps!