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  • Writer's pictureGautam

Non CO2 aquarium a.k.a Low Tech Planted Aquarium

During my various interactions with hobbyist, nature aquarium enthusiasts over the year, a topic keeps popping up pretty consistently. There are many names to it, ‘Non CO2 Aquarium’, ‘Low Tech Planted Aquarium’ etc. etc. This blog post is to add my two cent on this highly debated topic.

Let me start the topic with a story from the master nature aquarist – Mr. Takashi Amano. In his seminal work “Nature Aquarium World” there is a section titled “Five Bottes of Carbonated Water”. In this section Amano writes that while his journey with creating planted aquariums started way back in 1977, but then the results were not very encouraging. He discussed with his mentor, Professor Nagashima and understood that 0.03% CO2 should be enough. Amano weighed options like using dry ice. Then finally as it happens with many of us – a trip to the local bar finally did the trick. The label on carbonated water bottle – “water, carbon di oxide, NaCl (1%)” gave Amano the idea of using soda water in his planted aquariums. He got results immediately as his plants started photosynthesising. Amano writes “If I hadn’t discovered that carbonated water …, I surely would have given up the whole idea if aquatic plant aquaria”. So all of us in the planted aquarium should be indebted to the soda water bottle.Jokes apart, the story basically emphasizes the importance of using Carbon dioxide in planted aquariums.

Coming back to the main topic. So what are the common ways of providing CO2 in planted aquariums:

1) The age old DIY method of using yeast and sugar or

2) Using pressurised CO2 cylinder.

While those who have tried the first option (and its variants like using baking soda) are aware of the hassles involved, the second option definitely has significant cost involvement. Yes, there are low cost alternatives of pressurised CO2 systems available in the market but then there are risks involved. Maybe will write about that in a different blog. So it’s not surprising that people often ask me this question can we not have a non CO2 planted aquarium. The hobbyist’s version of the same question is what are the options of low tech aquarium. My answer is pretty simple. Plants need carbon to photosynthesize. Without carbon the plants won’t grow. So the question actually is how can we provide carbon without using external CO2 sources.

Here is what I do to grow plants when I decide not to use pressurised CO2.

1) Provide some fresh water every day in the aquarium

2) Slightly overstock fish

3) Reduce the KH (Carbonate Hardness) of water. I am assuming usage of de-chlorinated tap water here. I use ADA Aqua Conditioner Soft Water ( for this purpose. As the following chart shows that for a given pH the CO2 concentration increases as KH goes down.

Figure 1:

4) The other thing that I do is keep the temperature low. The following chart clearly suggests that for a given pH, CO2 concentration goes down with increased water temperature

Figure 2:

Here are some examples of planted aquariums using the above method.

Non-CO2 Nano Aquarium

( Image Courtesy and copyrighted to: Ripples, Visit at: )

Non-CO2 Large Planted Aquarium

( Image Courtesy and copyrighted to: Ripples, Visit at: )

The other option for having a non CO2 planted aquarium will be to use plants like some species of Echinodorus or Vallisneria which has the ability to assimilate carbon from bicarbonates of water. In this case however you should not reduce the KH of water.While we learnt about the use of soda bottles as a CO2 source. I will recommend not using them as over time sodium concentration will grow and will be detrimental to plant growth.The other aspect that one needs to note is that Patience is very very important to set a non CO2 induced planted aquarium. You see no one injects CO2 artificially in natural water bodies where aquatic plants grow. So how does plant get carbon. The answer lies continual decomposition of the substratum in these water bodies. Various forms of carbon and it’s derivatives gets produced due to bacterial activities in the substratum. Going by the same analogy if one allows the substrate in a planted aquarium to age then the substrate itself becomes a source of carbon over time. Greatest examples are the dirt tanks of Ms. Diana Walstad. Even Amano has observed during his early days of planted aquarium, “I realized that while I could raise plants fairly successfully in old aquaria, the newer ones were just no good”. Even when I was young I have seen plants growing even in old sand in some of the LFS tanks.


Will like to end the article with my observations on some of the so called Liquid Carbon products available in the market. I believe these chemicals are nothing but Glutaraldehyde in some form and in long run does more harm than good in planted aquarium. Isn’t it natural if it has ill effects on human health (read this then what it can do to the fish and micro fauna of the aquarium. In small doses Glutaraldehyde acts as an algaecide, so it basically eliminates algae on plant leaves. With this happening photosynthesis improves slightly but then at what cost? The article from Sunken Garden explains this aspect very nicely -

So my friends it is not at all advisable to use these liquid carbons in aquarium. You see we are trying to create a natural self-sustaining ecosystem where micro fauna plays the most vital role and I am 100% sure the liquid carbons will never allow micro fauna to stabilize and hence actually never supports a planted aquarium or nature aquarium on the long run.


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