The 3 Pillars of Successful Planted Tanks + CO2 Diffusion

The Planted Tank If you’re just starting a planted tank, you’re likely trying to figure out specifically what you’re supposed to be doing. You’ve heard about proper lighting, this thing called ‘Watts Per Gallon’ and PAR, injecting CO2 (or not), and apparently ‘dosing’ your plants.

This article is meant specifically for you. Take a look. The basics are explained here, and are descriptive of what’s actually happening when you’re doing these things.

Nutrients in the Tank

Every tank needs four things: Nitrates, Phosphates, Potassium, and ‘Micros’ (trace-level compounds that plants use.) These are the compounds that plants use to do what they do everyday: take in CO2, and give off oxygen. (Side note: when plants give off oxygen, you’ll see tiny bubbles coming off them. This is called pearling, and is a sign of a great tank!)

You can measure the levels of these nutrients using test kits. There are kits sold for individual compounds, but do yourself a favor and get an all-in-one. It’s the best you’ll find, and I’ve used these types with great results for a very long time:

Use one of these to determine the levels of following compounds:


Nitrates are used by plants to make amino acids, which are then converted into proteins—the ‘building blocks’ of plant materials. Essentially, this is the ‘stuff’ that plants use to physically grow themselves. For most tanks, you’re targeting a range around 5-10 PPM (parts per million).


Phosphates help plants prevent disease and stress by distributing the energy produced throughout the plants. If they don’t get enough Phosphates, they’ll be stunted and noticeably pale. Keep this parameter around 0.5-1 PPM, or roughly 1/10th of your nitrate levels.


Potassium is essential for healthy growth. In plants, it regulates the intake of CO2, which means it determines how fast and healthy the plant grows. It also begins the entire process of sugar production. You’re looking to keep the water at around 20 PPM for Potassium.


‘Micros’ are nutrients that plants use in such small amounts they’re not necessarily ‘measureable’. These are called trace-level nutrients, and include Calcium, Magnesium, Sulfur, Boron, and even Chlorine. You’ll likely want to use a catch-all dosing method for these nutrients. Most aquarists use SeaChem Flourish, which includes all the various compounds that plants are looking for. The amount of Flourish you put in your tank depends on the size. Generally, you’ll want to use 1 capful (around 5 mL) for every 60 gallons twice per week. If you have a smaller tank, the threads on the cap are markers for every 1mL.

Lighting in Planted Tanks

This is what determines the success or failure of your tank. Most non-aquarists assume that the light included with their tank is adequate for growing plants, and wonder why every plant they buy just withers away.

99% of the time, there isn’t enough light.

The following rule is a very basic guide. I’d highly suggest using the PAR value of your light as a better guide; this is simply intended to be a rough estimate of your current lighting conditions:

A general rule to follow in lighting your tank is what’s known as the Watts Per Gallon rule. Here’s a general breakdown:

  • 1-2 Watts: Low Light
  • 2-3 Watts: Medium Light
  • 3+ Watts: High Light

Note that this is a general concept. Your plants may need a specific amount. You can do some research on your preferred plant type for more information.

PAR Value

A better way to measure lighting is with the PAR value of the light. You can find this on the box of most reputable lighting brands. Here’s a small chart:

  • PAR 10-30: Low Light
  • PAR 30-80: Medium light
  • PAR 80-120: High Light

This is a more accurate way to gauge your lighting conditions and needs in your tank. You’ll find both used somewhat often in forums. Remember, the best thing you can do is ask questions! Feel free to ask us questions on our Facebook page, or start a thread on the PlantedTank forums.

You’d be surprised how well plants can do simply given enough light. However, when doing this, you’ll need to be sure and balance out the other two pillars of your tank to keep algae from taking over.

CO2 Diffusion

This is the facet of Planted Tanks that gives most people trouble. Whether it’s the danger of CO2, the potent ability of CO2 to efficiently kill your fish, of the inability to definitively ‘measure’ the CO2 level, most tanks don’t get this right.

However, it’s not hard. It simply requires some patience and understanding of what’s actually going on in your tank’s system. Here’s how it works:

Water naturally has some amount of CO2, but it doesn’t have nearly enough to supply plants with enough carbon to grow at a satisfactory rate for most Aquascapers. Thus, we need to add it somehow.

We do this by creating some system to diffuse the CO2 into the water. This is done with a diffuser. These create miniscule bubbles of CO2 which are (mostly) absorbed by the water.

The downside to using CO2 is mainly its costs. Regulators and tanks can regularly cost $125 or more. It’s worth it, though. When CO2 is used correctly, your plants seem to explode in growth!

As far as CO2 hardware goes, If you’re going to use CO2, get a quality regulator. I can’t emphasize this enough, you don’t want your tank emptying its CO2 into your house, because that can get quite expensive. This is what’s known as an ‘end of tank dump’, and it happens to lower quality regulators.

Don’t let that scare you, though! It can easily be done safely. There are two options: DIY (do it yourself), or using a CO2 tank. DIY is usually used for smaller tanks, and the CO2 tanks are generally reserved for larger aquariums. Both techniques end up inserting the CO2 into the water through a bubbler, which helps you measure how much CO2 you’re inserting. You’ll often find this referenced as ‘bubbles per second’. Most kits include the equipment for this, including the two I’ve linked below.

However, I’d advise you to use a CO2 tank and kit, if you have the budget. Nothing beats having a product that is specifically made for doing this.

You can find a few good ones here:

Bringing It Together

I’d advise you to get into a routine when you first start a planted tank. Do daily visual checks to see if any plants are browning or dying, check your CO2 rate on your bubblers. Do weekly water changes to keep your nutrients in check, and also check the levels on those nutrients with test kits. Finally, do monthly systems checks to make sure your equipment is working properly and nothing’s coming loose.

Do this, and you’ll be well on your way to a healthy and happy planted tank!

5 thoughts on “The 3 Pillars of Successful Planted Tanks + CO2 Diffusion”

  1. Hello,

    This is really handy. I wish I had done more research before starting my first tank. But it’s all a good learning exercise.

    That said, for round 2, it would be really handy to have a table, with tank size as row headings and columns for light intensity, light duration, co2, filter type and throughput and nutrient requirements, and maybe recommended/max fish stock (in terms of collective length without tails; I heard that’s a good metric?). There could be sub rows for heavily planted and lightly planted. Somebody must have this information somewhere, it would be good to have it all in one place, tried and tested. For example, if I’m looking at getting a 180L tank, and planting it heavily, do I need CO2? If so, how much? There just seems to be a lot of advice out there for people having issues (like me), but not enough stats on what actually works well so we can get it right in the first place.

    Or as there are so many different combinations, have some model tanks we can aspire to?

  2. For those of us with “easy” plants, like anubias and java fern, is it still worth it to have a CO2 system?

    I’ve thought about boosting my CO2 by cutting my tap water with re-mineralized distilled to lower the pH and thus raise the CO2. It’s a 5.5 gallon tank, so it could be done with a standard bucket or two. I got that idea from seeing a chart that estimates CO2 from pH and KH. I’m not sure how feasible that is. What are your thoughts?

  3. Good article but you forgot to discuss substrate? Read separate article ok… But I would have written it as “four pillars” 🙂


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