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Newbie Needs Help with CO2


New Member
12 Jan 2022
Hello All,

I am an absolute newbie to aquarium hobby. After doing a lot of research I built my first ever aquarium 4 weeks ago, which is heavily planted. It has now been cycled and I have recently introduced some basic starter fishes in it. (Neon Tetras, guppies, Corydoras)
Its a 180Litre aquarium (101x50x40cm). Its the new Juwel RIO180. It has 2 LED lights (24watts combined, 1 day light and 1 nature light) and a 1000L/H internal filter. It has 4 layers of substrate (Gravel + Volcanic curshed rocks + Aqua soil + decorative sand). Most plants are root plants.

Since I want my aquarium plants to look healthy and this is supposed to be a low-tech setup with minimum water changes as I want plants to do the heavy (nitrate) lifting, I want the plants to grow in a healthy manner. I am thinking about getting a CO2 system without spending too much money. I am struggling to figure out exactly how much bare minimum CO2 my tank would need for my plants to thrive. I am looking for your expert advice in terms of, What tank size should I go for that can provide bare minimum CO2. When I say bare minimum, I mean enough amount that my plants need every day for a set number of hours. (Maybe 1 bubble per second for 7-8 hours).
Keeping this in mind, what CO2 tank size should I go for? I see people recommending 2kg and that it lasts around 5 months or so. I need to know if that's correct or a 500gm tank could deliver same results. Also I am assuming 2kg and 500gm is the weight of the tank? One tank I am looking into has 8L CO2 capacity.

I am looking into buying used CO2 systems with CO2 tanks that have long life left in terms of expiry. I also looked at the DIY Co2 systems in which I would need to make solution every 4 weeks or so.

So knowing my case above, what would you advice? I can get a decent used complete CO2 system with CO2 in it for around $130 range. A new DIY system costs around $180+ and I think a totally new system would cost around $400+ which I find way to much to spend when used can deliver similar results for way less.

Desperately looking for your advice in terms of what should I go for and how long would a tank (500gm or 2kg) would last if I would go for 1 bubble per second for 7 hours a day.

Attaching my first ever aquarium picture for plant density reference. Most plants have yet to grow big as its a fairly new setup. Also I am just starting so please dont judge too harshly :)
Thanks :)


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6 May 2021
Some short remarks:
  • The number of bubbles is irrelevant and only serves as a reference. Do not compare bubble counts. Each setup will display different bubble counts. Most importantly, the bubble count says absolutely nothing about the CO2 concentration in the tank and the amount of CO2 that the plants are actually getting.
  • What matters is injecting a suitable amount of CO2 so that the CO2 level is stable during the day, which means the plants are getting the amount they need. The actual amount of CO2 you need depends on multiple factors, including light, plant mass, surface agitation, diffusion method. Read <this> and <this> as a starting point as well as the remaining 2hr aquarist articles on CO2. Plenty of extremely informative threads in UKAPS on CO2 as well.
  • For a 180 liter tank I would suggest at least a 2Kg cylinder, ideally a 6Kg or 10Kg. Get the larger cylinder that fits in your cabinet (a 2Kg will certainly fit). You really do not want to be refiling cylinders every few weeks.
  • 2Kg of CO2 means the amount of compressed gas inside the cylinder. The total weight of cylinder is much higher. A cylinder with 2Kg of CO2 weighs 8-10 Kg (6Kg CO2 -> ~20Kg cylinder, 10Kg CO2-> ~30Kg cylinder).
  • Read <this for same examples of CO2 usage>. Your actual injection rate and CO2 usage will be unique to your own system. So do not generalize.
  • DYI CO2 works well for nano tanks. But a DYI system in a 180 liter tank is not be sufficient to generate sufficient (and stable) CO2 to reach the recommended concentrations (around 20-30ppm). A small amount of DYI CO2 will surely help the plants, but it will all depend on your goals with the tank.
  • In Europe you can get a good quality complete CO2 system (2Kg cylinder, single chamber regulator, needle valve, magnetic solenoid valve, in-tank or inline diffusor, and pipes) for ~180 EUR. A similar system with a double chamber regulator costs ~250 EUR (you can ask later about the difference between single and double chamber...)
  • A CO2 refill should cost you around 20EUR (the price is virtually the same for 2 or 10Kg - you are basically paying for the service). You should check what are the options for refilling CO2 in your area. Some large hardware stores offer a refill service but usually you also need to buy the cylinder there. Companies that deal with industrial gases usually refill any cylinder if the certification is still valid. Not sure how this works in the NL.
  • Very nice tank, btw!
Last edited:


16 Jan 2021
From the picture it looks like your water level is too high. Is that the central brace I can see below the water line? This would probably hinder water movement on the surface.

I've been in the hobby a couple of years, the key point with co2 that I'm getting the hang of only now is - LOTS of surface movement and high injection rate. It's not really worth trying to conserve co2, your plants will only suffer ...

With regards to finding a co2 supplier, I highly recommend finding a fire safety company, usually they have loads of expired extinguishers that they're happy to give away or sell cheap. From my local guy I can get a 2kg extinguisher for only £5!

Good luck, take your time to learn and figure out what works for you!