The Secret To Growing Red Aquarium Plants

The Secret To Growing Red Aquarium Plants

Needle Leaf Ludwigia

The Secrets To Growing RED Aquarium Plants

Fish Tank Mike
Renowned Fish Tank Designer and Red Plant Enthusiast 🤠  

Red aquarium plants are a coveted aspect of the planted aquarium community. There are many types of plants which are innately red, if given the proper conditions. Some are easier than others and we will discuss not only the most important factors in establishing a deep red coloration but also what the best options are for the beginner planted tank enthusiast. Don't forget that not all aquarium plants ave the ability to become red as it is a genetic trait of a particular subset. However, many aquarium plants that at first seem to be exclusively green will transition to fully red or partially red if the correct conditions are met. At the end of the day, high tech aquariums with added CO2, strong lighting and fertilizers will always result in healthier and potentially redder plants. 

CO2 Plays A Vital Role

Carbon dioxide plays a vital role in aquatic plant development, growth and phenotype. Many plants that appear green will transition to having red accents or even become completely red when adequate CO2 levels are provided. 

For most planted tank keepers, somewhere between 20-40 ppm CO2 ends up being the perfect amount. The goal is to add enough for the system to be replete with CO2, nothing more and nothing less. Too much CO2 can cause fish to gasp for air and potentially result in death. Luckily, plants themselves don't seem to be adversely affected by extremely high levels.   

In a previous experiment, we built two nearly identical aquariums with the same plants, light source, substrate, etc. The only difference was the tank on the right had approximately 30 ppm CO2 supplemented via a pressurized system. The tank which had added CO2 resulted in not only faster more developed growth, but the Rotala red was drastically more red when compared to the tank on the left which had no added CO2. It's hard to see in the image, but even the Hygrophila compacta var. in the center rear which is typically a green plant displayed red coloration at the points of new growth.  Plants such as the baby tears in the front of the tank remain green because they simply do not posses the ability to turn red no matter the conditions.  

Interestingly, the Ludwigia needle leaf (stem plant in front of the Rotala red) did not turn very red as a result of adding only CO2. Take a look at the very first image in this article, that is the same plant in a tank with CO2 AND a very high powered LED. So while CO2 obviously help plants grow faster while simultaneously influencing red coloration, it's not the end all be all. Some plants, for example the needle leaf Ludwigia seem to require more than just CO2 supplementation...   

If you are interested in using a pressurized CO2 system on you planted aquarium, check out the CO2 products within our buyers guide for more information. There we have selected a number of different parts and even full kits to get started using CO2.

Intense Lighting 

While CO2 seems to play a role in a plants ability to express red coloration, it's definitely not the only factor (needle leaf example). Light intensity definitely plays a role and is what most aquarists think of when determining why some of there plants are red. We notice that even in non-CO2 supplemented tanks when certain plants get close to the top of the water column, i.e. closer to the light, the tips will begin to turn red. The rest of the plant below will almost always stay the original green color, hinting that the proximity/strength and wavelength of the light is the cause.   

In today's age, most all brand name aquarium LED's will create an intense lighting scenario at depths up to 20 inches. Some great choices for powerful aquarium plant LED's can be found below: 

Fancy Powerful LED

ONF Flat One+ LED

Budget Powerful LED

Current USA Serene Sun Pro

What About Iron?

Iron (Fe) is an obvious candidate, its a vital micronutrient for all aquarium plants and is found in many areas of the cell. Most notably it's co-factor in many enzymes that are required in pigment generation and thus the expression of red coloration when possible. Hobbiests often say that Fe supplementation is one of the main factors in turning plants red. While I don't think that statement is wrong, (it defiantly plays a role) I do believe and have observed myself, plants can easily become red without supplementing extra Fe. This does not mean that my plants don't have access to Fe, I'm just not adding much extra via liquid fertilization. 

Fe is important, some tanks I add laterite clay in the substrate to provide more via the roots. Some of the liquid fertilizers I use contain small amounts of it as well. However, I have never found myself in a situation where I wanted a plant to express more red color and used extra Fe to achieve it. It always comes back to the CO2 and lighting, that's where I find the most dramatic shift in plant coloration. 

Easy Beginner RED Aquarium Plants

rotala red aquarium plant

Rotala Var. red

ludwigia natans super red aquarium plant

Ludwigia natans super red

ludwigia repens red aquarium plant

Ludwigia repens

Use Code aquaprosBP on Buceplant to save 15%

That's going to wrap up today's discussion on how to grow red aquarium plants. I hope this article help nail down a few concepts and pushed you in the right direction. If you have any questions please leave them down below in the comments section and we can chat about it! Thanks for taking the time 🤠

-Fish Tank Mike 

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Actual CO2 isn’t liquid except at pressures found only in pressurized vessels (just like nitrogen, which is normally a gas, but can be pressurized into liquid nitrogen), you are referring to the disinfectant glutaral, which is the active ingredient in “liquid co2” additives like excel. There’s plenty of debate about how it works, and if plants are able to extract any carbon from it, or if it simply clears algae and microorganisms from leaf surfaces providing more light and available nutrients to the plants. That being said it does kill hair algae like nothing else, which is definitely beneficial if you’re experiencing an outbreak like I was for the short time I tried using it, and though I didn’t notice a difference in plant growth while using it, it didn’t hurt anything either and even at higher doses didn’t bother my fish, some of which are very sensitive, supposedly. I currently dose liquid fertilizer weekly, add fertilizer tablets every few months and had vigorous green plant growth even at 24 inches below my 6k LEDs, but my red plants were turning green and melting, until I added a second high output LED that had both red and blue LEDs in addition to just white. My red plants exploded in growth and color and look better than when I picked them out at the store. I truly believe red plants need red light, or at least a more complete spectrum, and there’s plenty of aquarium owners and online articles that agree. All my tanks use finnex lights, I highly recommend them. I use API leaf zone liquid fertilizer and seachem flourish tabs for my substrate which is sand. And I don’t plan on supplementing co2 at all, I actually use air bars at the back of the tank for increased flow and aesthetic value as well as multiple fluval circulation pump powerheads to ensure constant flow, no dead spots, and gentle leaf movement (makes stems stronger just like wind does in terrestrial plants) so I actually have a deficit of co2 compared to other low tech tanks.
And, I don’t know if it effects plant growth, but I have extremely hard water (like 120+ tds) and I over filter by 200-300 percent the recommended filtration for my tank sizes in both mechanical filtration as well as biological filtration via air driven sponge filters, which I supplement monthly with Tetra cleaning bacteria. My water has been crystal clear going on 5 years in all of my tanks, and I regularly have to trim plants back and give away the inevitable new plants that keep popping up.


Jim- I have not done a direct comparison between liquid vs gaseous CO2. That said, I think it would be fine for you to test out the Seachem Excel and see how it goes, just be consistent in its use. Using a pressurized CO2 system will always be better in my opinion, how much better? Can’t for sure say.


With the side by side comparison, have you done a test with a CO2 system compared to a liquid co2. For those just getting the plant bug and don’t want to commit to a system yet.


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