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Aquarium Plants Discussion

Aquarium Plants: A General Discussion

Article by: Brian Marais

There are a plethora of plants to choose from for your aquarium. Some are very easy and are commonly referred to as weeds in aquariums, while others are so tricky that the closest comparison I can make is that they are as sensitive as discus; one funny look from you and they could just die. 

And with all the equipment requirements from lighting, CO2 injection, fertilizers, etc., it’s little wonder why so many people struggle to keep plants alive in an aquarium. Often is the case that this new technology doesn't make it any easier; if often makes it more difficult where it really shouldn't be the case. In this article I am going to explore why this could be. 

I am going to attempt to put your minds at ease regarding planted aquariums because, for all the nuances related to aquarium plants, there is common ground amongst them all that really do need to be in place before we can see successful aquatic gardening come to life. 

For those of you who have planted tanks, I am sure that most of you are trying to emphasize the plants and not necessarily the fish? I could be wrong, but still, for what other reason would you have plants in your tank besides as an additional means of filtration? 

There is so much science that goes into plants that one could easily argue that they can become more difficult to keep alive than corals. After all, corals form part of the Animalia kingdom, where plants are from the Plantae kingdom, and each have very different physiological processes that keep them alive. We’ll explore some of these processes later, and I will try to keep it simple to understand. But generally speaking, plants are unique not only in appearance but also in these biological processes that they can sometimes be considered alien. I can understand that point, as plants assimilate nutrients in different ways than humans that when viewed microscopically, the point can be easily validated. 

There are building blocks to set when it comes to setting up a planted aquarium. Let’s get started with the foundation and work our way up from there. 


Gravel is perhaps one of the most important building blocks, but often is overlooked. I think the reason why it is overlooked is due to its price. Most nutrient enriched gravels for tropical aquaria are expensive and, coupled with the fact that one could need several bags to layer the gravel sufficiently, the total price often borders on the ridiculous. 

Fret not, because there are methods that don’t involve nutrient-rich gravel. However, these are perhaps a little more difficult as the plants would rely heavily on you to provide the necessary nutrient by means of liquid fertilization. We’ll discuss liquids fertilizers later. 

Why is nutrient-rich gravel so important? Well, to explain that properly, one would need to know how nutrients behave and react in water. In a nutshell, these nutrients are designed and compiled in such a manner that plants can easily access them via their root structures.  They are not only iron-rich, but also contain many of the nutrients that plants need in order to grow and thrive.

Let me digress for a moment here to tell you about plant nutrients. There are 2 sects of nutrients that plants need in order to flourish and they are Macro Nutrients and Micro Nutrients.  

There are 3 macronutrients, namely Potassium, Nitrogen and Phosphorous. You’d have to add carbon to these as well, as carbon is inherently important for all life on Earth. Without these nutrients, plants will not flourish and will die in time. They play an integral role in plant biology, in that they allow the plants to grow, stay healthy, and assimilate other nutrients more efficiently. Think of these nutrients as your staple diet, which could consist of nice ratio of protein, starch, firbre, vegetables, etc. Most of these nutrients become readily available in aquariums in any case, however, they may not be enough for the plants and may result in nutrient deficiency and even total depletion. Nitrogen, for instance, would become present for plants during the natural processes that take place to break down waste (nitrogen cycle). Ammonium, Nitrite and Nitrate all consist of Nitrogen, which the plants can use. Some plants can be selective with regards to the form of Nitrogen that it utilizes. Some plants prefer ammonium, while others prefer nitrate. These forms of nitrogen, however, may become difficult for the plants to assimilate, in that they may expend more energy assimilating them than the nutrients themselves could provide. 

Micronutrients are the nutrients that plants need in small doses. These include Boron, Calcium, Copper, Iron, Magnesium, Manganese, Nickel, Zinc, Chloride, Molybdenum and Sulfur. Some of the major ones mentioned above are Magnesium, Iron, Calcium and Manganese. Think of these nutrients as your multivitamins. 

Magnesium is a key component of chlorophyll. Iron plays its role as a transporter of enzymatic electrons and Manganese is essential for the decomposition and separation of molecules by means of light in water (a process known as photolysis). Calcium is important for maintenance of membrane structures and permeability and for the formation and stability of cell walls. Like I said before, there really is so much science at work when it comes to plants. 

Getting back to gravels, the key things you should look for when purchasing gravel are the following:

  • The gravel must offer a wide range of macro and micro nutrients
  • Must be porous
  • Gravel should not break down over time into a powdery form. This is important because gravel that does this could end up suffocating your plants. 


Good lighting for plants will include a broad range of colors from the colour spectrum. It isn’t uncommon to find that a lot of people use light that is slightly yellower in appearance along with something slightly bluer. 

Plants utilize a range of colours except green. Plants - in fact, chlorophyl - are, for the most part, green and thus reflect green light. So a purely green light will be nothing more than useless for plants. Good colours to look for in a bulb or lighting solution are red, white and blue, and a little bit of yellow.  

Red light has a long wavelength, which means that it loses its intensity in water the further it has to penetrate. Blue light, on the other hand, has a far shorter wavelength and can penetrate far deeper than red light can. Now there is some concern among aquarists that algae utilizes blue light and hence, a tank that has blue light over it will be cursed with algae issues. While this is not false information, as with the grapevine effect I often speak about, there is some information missing here. 

Blue light cannot only be used by algae but is, in fact, gobbled up by plants as well. Truth be told, in the absence of blue light, plants tend to grow tall and “leggy” (where the spaces between nodes are extensively separated). This results in a plant that does not look pleasing to the eye. In the presence of blue light, plants grow out fuller and the spaces between nodes are actually close enough, resulting in a plant that is bushier and far more attractive. If you do experience algae issues in your tanks, then it is more than likely that some or other underlying issue is causing it, and not just due to the presence of blue light. 

Lights should be on between 8 and 12 hours per day. If you are experiencing algae issues, I would start by slowly reducing the photoperiod until it disappears but still yields good plant growth. As with any troubleshooting with aquariums, it is worth doing things slowly. 

Lights should be strong enough to penetrate the water, and enough intesity at the bottom of the aquarium to provice sufficient solar energy to plants and leaves at the bottom. If the lighting is not strong enough, a typical indication would be that the plants grow bushy at the top, but lose their leaves at the bottom. 

So how much light is enough light? Well, that would depend on the plants you're trying to keep. Some plants require so much light that it would burn plants that don't. You should be aiming at about 1 watt per litre of water for plants that require high light. 0.5w/L would be considered medium lighting and anything less than that would be considered low lighting. Now is a good time to throw a spanner in the works: Tanks that are very deep - from about 700mm and up - would require specialist lighting. By this I mean Metal Halides or LED's.

Metal Halides are potent and have enough energy to reach as far down as a meter. The problem with them is that they are not only expensive to purchase, but are also expensive to run. These lights draw a lot of power to run and also need to be replaced every 8 months or so. LED's, on the other hand, are very expensive to purchase but, if looked after nicely, can last anywhere between 10 and 12 years, without the need to replace globes. They also draw far less power than your typical bulbs, such as Metal Halides, T5 flourescents, Halogen globes and Mercury Vapour. Bad things happen, and even with your nice expensive LED unit, you may need to replace a single LED or two to get it work again, or replace the cooling fan, etc. These things happen, but maintenance and proper care of the unit should limit potential problems later on. You'll definitely see how these lights can save you money in the long run. 


Fertilizers in a liquid form are more commonly found in aquarium shops than are most other forms of fertilization. You will also be able to find what are known as “root tabs,” which are small tablets that are inserted into the gravel to allow the roots to take up nutrients through them. 

Earlier I discussed that it is possible to grow most aquarium plants without nutrient-rich gravel. This is where liquid fertilization and root tabs are required, and it will need to be quite extensive as well. Iron, for instance, is an element that is taken up rapidly by plants and is very important for plants’ biological functions. Without a nutrient-rich substrate, one would need to dose a liquid iron source for plants to utilize. Without any of this, most of those brilliant red plants that we love so much will lose their colour. For example, Rotala macrandra or R. wallichii will fade away in time without iron. There are other reasons why these two plants could suddenly lose their colour or turn green, but that won’t be discussed here. 

There are a multitude of fertilizers on the market and it is really a matter of personal choice here. However, that said, I do feel that there should be things to look out for in certain types of fertilizers. For instance, iron supplements should come in a ferrous iron form, which is soluble in water. The reason for this is because plants need to first break down ferric iron - Iron (III) - into ferrous iron - Iron (II) - before they can be absorbed. A ferrous gluconate form of iron is best absorbed by leaves. This is particularly true for dicotyledenous plants, but in the case of monocoytledenous plants this works slightly differently. Monocots do not reduce iron to the ferrous form, called Iron (II) before transport. This type of plant reduces iron to its ferrous form in the cell cytoplasm later. This is why they tend to expend too much energy to convert Iron (III) to Iron (II)

I fear I may have already lost some of you who have little to no interest in this, but the bottom line is that the best form iron to provide is Ferrous Iron, or Fe(II), because plants won’t need to expend a lot of energy to gain a useful source of iron. 

In fact, any product that can allow plants to assimilate both micro and macro nutrients without the need to expend energy to do so would, in my opinion, be a good thing to look for in any liquid fertilizer. 

CO2 Injection

Let’s get into the subject of Carbon Dioxide (CO2) injection. Is it worth the fuss, or is it a needless expense that can be overcome by some other means? Before I go into that, let’s first talk a little about photosynthesis. 

Photosynthesis is the process by which CO2, water and light energy are utilized to create glucose and oxygen (O2). For those who are interested in this, the equation for this is as follows:

6C02 + 12H20  ---->  C6H12O6 + 6H20 + 6O2

Carbon dioxide + Water ---> Glucose + Water + Oxygen

Seeing as our planet is filled with carbon-based life forms, it would make sense to add a source of carbon for your plants to grow. How that carbon is introduced is a matter that can be debated forever and a day, but the crux is that plants need CO2. Many people ask whether the plants get their CO2 as the product of fish respiration. The answer is “yes”. However, the amount CO2 produced by fish, in most cases, falls far short of the plants’ requirements. This is true even when plants are required to extract CO2 from the atmosphere. CO2 is rapidly taken up by plants, which then get used to create a host of other complex compounds. Because it is so rapidly taken up, plants limit their own growth because of the lack of carbon.

In my opinion, I’d say that a good CO2 unit is needed, even to grow the easiest of plants. There is the expensive, yet more reliable way of doing it, and there’s the inexpensive and often laborious method that involves a process of fermentation. There is also a liquid product by Seachem called Flourish Excel, that adds an organic source of carbon that will not only allow the plants to assimilate easily, but will also not alter your pH, where normal CO2 will. 

In short, adding a reliable source of carbon into your tank is definitely needed, regardless of how quickly your plants can assimilate it. The reason why is that fish respiration, organic waste products, etc., will not provide enough carbon for your plants to grow quickly. For some further reading on the subject, I recommend that you delve into some research on the Carbon Cycle, which is easily found on Google or Google Images. Basically, in nature, plants have near endless reserves of carbon as it makes its way through the soil and into the water systems. In an aquarium, it is literally impossible to create this cycle and for that reason, CO2 injection is important. 


There are so many aspects to keeping plants, but I hope that I have provided a general idea about them. Each plant has its own set of requirements and each has a unique beauty. Some are far more difficult to keep than others while some plants grow like weeds in even the simplest of aquarium setups. 

The topic of plants and their care is so diverse that one cannot write a short article on the topic. There are some things above that I have omitted from the article that play important roles as well, such as General Hardness and pH. These are entirely different matters that do need to be taken into consideration, but what I have mentioned above are merely the basics. If you can get the basics right, then keeping plants becomes far less a pain than most people tend to think. Planted tanks perhaps go against my general rule of thumb regarding aquariums, and those who have met me before will probably have heard me say this: “Don’t add any supplements to your aquarium unless it is needed.” 

Well, for tropical tanks it works the other way around. I have shown the importance of building a good foundation with gravel and dosing supplements. Planted tanks are the only types of aquarium, in my opinion, where my rule is debunked and dosing the tank daily with quality fertilizers is, in most cases, a requirement. 

I'll explain more about plants and, in particular, pH and GH, in a later article. Please, come into the store and chat to some of our staff about what you've read, or share your experiences with us. It is always great to learn new things, which is what I hope to have achieved in this article. 





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