When I bought my first fish tank in my teens, I was daunted by keeping live plants, so I opted instead for plastic replicas.
My favorite of these was a green and red broad-leafed imitation which was quite realistic and added a welcome splash of color to the aquarium.
Little did I know, then, that it was a replica of a plant so easy to grow that I could have just planted the real thing. That wonderful plant is Ludwigia repens.
Origins and Background
Ludwigia is a family of temperate–tropical amphibious plants from the Americas. The genus belongs to the Evening Primrose family, hence their common names – water primrose or primrose willow.
Ludwigia repens is specifically known as creeping primrose-willow, owing to its creeping stems, which send out roots when the plant contacts a suitable substrate. This prolific reproducing method has even become a weed in some American waterways!
While Creeping primrose-willow is famous in the aquarium trade for its reddish color, it can also grow in green or brownish shades or a combination of these three.
Size and Growth Habit
Ludwigia repens stems grow 12-20 inches tall by around 2 inches wide. This means that vigorous specimens may breach the surface of a shallow aquarium.
When growing in low light, this plant may become quite ‘leggy’ – it will shed its lower leaves and form long thin shoots to reach brighter light nearer the surface. However, the plant will make a lovely bushy form when given higher light levels.
Their growth rate also depends on the amount of light, carbon dioxide, and fertility available, so let’s take a closer look at those here…
Ludwigia repens is only moderate in size, so it will grow happily in a 10-gallon tank. It also looks stunning planted in quantity in much larger tanks.
Some enthusiasts in warmer regions have even introduced this plant to their ponds – although this is a doubtful practice, given the plant’s propensity to become invasive!
Ludwigia repens prefers soft and slightly acidic water but is remarkably unfussy and can survive perfectly well in harder, more alkaline waters.
This is also true of its temperature requirements! Whereas the plant prefers water in the range of 75-79 Fahrenheit, it will also tolerate temperatures down to 59 Fahrenheit, making it suitable for the coldwater aquarium and tropical.
The Best Substrate – Sand, Gravel, or Soil?
Ludwigia repens is a tough plant that can survive in various substrates. For the plant to be at its best, it may be best to avoid sand, which can get so compacted that oxygen levels become depleted, and roots find it difficult to grow.
Gravels can provide good, aerated anchorage for your plants but are lower in nutrients. Fertilizers in root tabs may be necessary if you plan on growing lots of plants in your gravel.
The best substrate is soil if you want to go for the heavily planted aquarium. Good aquarium soil is specially formulated to contain a balanced blend of nutrients your plant needs to thrive.
A plant that’s given adequate nutrients in a good substrate will be more vigorous, with lusher colors and shiny, dark, healthy-looking leaves.
Proper lighting is perhaps the most critical factor for Ludwigia repens to be at its brilliant best. This species requires medium – very strong lighting.
If lighting is not strong enough, the plant’s colors will fade, and its lower leaves will fall off and rot at the bottom of your tank.
The simple equation with this plant is: more light equals more color! Light intensity brings out its dramatic red pigments, which is what most aquarists will look for in this plant.
In fact, varieties bred with deeper red pigments also demand more light just to survive.
Brighter light also helps the plant to become bushier and encourages healthy, colorful leaves right down the plant’s column.
Before you go out and buy the most dazzling bulbs you can lay your hands on, remember that light will also increase your plant’s photosynthesis rate and, therefore, its demands for nutrients and carbon dioxide.
Check out this excellent guide to aquarium lighting for plants here.
Ludwigia repens has fairly modest nutrient demands but will grow best if all nutrients are at optimal levels. It’s an alluring plant species.
Aquarium fertilizers come in three main forms – liquid, dry, and tablets, and are sometimes added by hobbyists hoping to boost their plant’s growth.
Whether or not your Ludwigia plants need extra feeding depends greatly on your tank setup and what you want from your plants.
Understanding Plant Nutrients
Aquariums naturally contain most of the nutrients that a plant needs to grow. They may need excess nutrients to develop strong roots. Strong roots are, obviously, good for increased strength.
Fish food, waste, substrates, and even ordinary freshwater are endowed with macronutrients such as phosphates and nitrates, trace elements, or micronutrients such as zinc, boron, and iron.
Macronutrients and Nitrate Requirements
Aquarium fertilizers labeled as containing macronutrients will have a mix of phosphates, potassium, and nitrates in the formula, which needs careful consideration.
Like all plants, Ludwigia repens need nitrates to stimulate the growth of lush, glossy-looking leaves. Providing plants with additional nitrates may be helpful in certain situations, such as in a young tank with low nutrient levels or when a plant’s growth is noticeably weak, with yellowing leaves.
It’s important to note, however, that nitrate levels above 2 mg NO3-N/l may cause harm to fish and invertebrates, so it would be wise to do a nitrate test before adding more.
Micronutrients are trace elements that are essential for healthy, resilient plants with robust immune systems.
Iron, for example, is essential to metabolism and will also help this species to display its deepest red colors.
If you’re looking to boost micronutrients without adding additional nitrates, go for a micronutrient-only fertilizer, such as Tropica’s Plant Growth Premium, or find a dry fertilizer in which the different nutrients come in separate packets. Apply micronutrients carefully and watch for results.
A Note on Copper and Invertebrates
Copper is an essential mineral for plant growth, yet most tanks will already contain sufficient quantities to meet your plant’s needs.
While some fertilizers contain additional copper, it’s essential to know that large doses of copper can be harmful or even fatal to invertebrates such as shrimps and snails.
If you decide to add any kind of copper compounds to a tank with invertebrates, be sure to pay attention to their health and make regular water changes to be safe!
So, Does Ludwigia Repens Need Fertilizer?
In a lightly planted community tank, Ludwigia repens may not require feeding. However, plants will benefit from macronutrients, micronutrients, or complete fertilizers to boost their growth in a more heavily planted tank setup.
For more information on choosing the right fertilizer, check out this detailed guide!
Does Ludwigia Repens Need Additional CO2?
All plants need carbon dioxide to photosynthesize, and submerged aquatic plants obtain it from dissolved CO2.
Some aquatic plant enthusiasts use CO2 injectors to boost their plants’ growth rates and all round vigor.
Ludwigia repens only grows at a modest rate and doesn’t tend to be especially hungry for CO2, but if you’re using higher levels of lighting, then additional CO2 may be beneficial.
As with fertilizers, it depends greatly on your particular tank and its inhabitants. Respiration in fish and microorganisms in your aquarium will already produce a certain amount of CO2.
In an established, well-stocked aquarium, it’s quite likely that your CO2 levels will already be sufficient for Ludwigia repens.
If you really want your tank to glow with masses of luxuriant plant growth, then increased lighting and CO2 injection will give you the edge.
Just make sure not to overdo it, as CO2 levels above 32ppm can be dangerous to your fish and other aquarium inhabitants.
Given optimum conditions, Ludwigia repens may grow away fairly vigorously, even breaching the water’s surface. Therefore, you might need to prune each individual plant.
Some aquarists don’t mind this, and I’ve even seen Ludwigia trailing off the outside edges of some tanks!
But if you wish to contain the plant, or to improve its shape, simply trim stems to two or three nodes above the substrate.
This will encourage lateral shoots to emerge from these lower nodes, and the plant will adopt a more bushy form.
You can either discard the trimmed stems or plunge them back into the tank’s substrate to grow again.
This method of producing a genetic copy of the parent plant is known as vegetative propagation.
Propagating Ludwigia Repens
Ludwigia is a very easy-to-propagate freshwater plant. This will obviously require nutrient-rich substrates. The type of substrate that will offer enough nutrients.
If you’ve grown this popular plant, you’ll have noticed the little root hairs that sometimes protrude from under the leaf axis.
This plant will also readily produce these from cut stems, which makes it an incredibly easy plant to reproduce.
Simply take a cutting, remove the leaves of the lowest two or three nodes and submerge it in the tank’s substrate.
Cuttings should grow roots and fresh shoots quite rapidly, meaning you can also share this plant with your friends!
Propagating by Seed
In the wild, plants of the Ludwigia family produce lots of tiny, four-petalled yellow flowers in the warmer months, followed by sinking seeds.
If your plant grows happily, with adequate warmth and lighting, it may also flower and bear seeds in the aquarium.
The seeds will naturally sink to the bottom of your tank and may sprout into new specimens.
It’s important to note that plants grown from seed will always be genetically different from their parents and may exhibit unique characteristics.
Although Ludwigia repens sold in aquarium stores have usually been bred for red pigments, its seedling offspring will be more variable.
Still, this variation can be a good thing! You may end up with some very green seedlings, whilst others could be the new prize-winners for their exceptionally red shades!
Companion Plants and Aquascaping
This reddish-colored plant will stand out even more brightly when paired with evergreen plants. It’s a fast-growing plant and can match well with other plants.
Red and green plants are on opposite sides of the color wheel, meaning the combinations of the two colors will really make each other pop!
Java Fern, Amazon Sword, and Hygrophila all have attractive green foliage of various shades and are also easy to grow.
Since it’s a medium-tall plant, Ludwigia repens look especially good when planted in a small clump in the center of your aquarium or en-masse at the back.
Some Java fern or Brazilian Micro Sword in the foreground could set it off perfectly.
Fish and Invertebrates Companions
As for fishy friends for your Ludwigia repens – you have a wealth of options! Any fish not renowned for destroying aquarium plants will make a good fit.
Most tetras, mollies, guppies, rasboras, corydoras, angelfish, and cherry barbs are all fine choices. Avoid aggressive fish species that love tearing up leaves, like Oscars and mbunas.
Think about fish species whose features will get highlighted against the red hue of this plant.
Silver and black fish like emperor tetra and zebra angelfish look stunning swimming alongside this beautiful plant and will enjoy swimming among its leaves.
These critters will love hiding in its dense foliage and can actually be beneficial to the plant’s growth by cleaning off layers of biofilm and algae that adhere to the leaves. This way, it can be a mutually beneficial or symbiotic relationship for both species!
Shopping for Ludwigia Repens
As I’ve said, Ludwigia repens come in various forms. Some may be olive green, while others will be an intense red. Cultivars with colorful leaves include ‘Rubin,’ ‘Super Red,’ ‘Dark Red,’ and ‘Ruby.’
To ensure you’re getting exactly what you want, compare plants in the store carefully.
Look for common aquarium plants with lush, healthy-looking leaves and strong colors. Beware of straggly plants with broken stems since they might harbor disease.
Ludwigia repens tends to transport and establish itself quickly, so don’t buy too many of your favorite plants! You’ll quickly have plenty if you follow our advice on propagation.
Just don’t get confused with…
Ludwigia ovalis, Ludwigia arcuata, and Ludwigia inclinata are cousins of Ludwigia repens and can all produce red foliage too.
Confusion among species, even among aquarium suppliers, is quite common! Take a close look at photos of Ludwigia repens, so you know what you’re getting!
Ludwigia repens is a conventional aquarium plant for aquascaping. Its robust nature and modest requirements make it a great choice for the beginner without a specialist setup.
At the same time, its glowing red hues will also satisfy the needs of the advanced aquascaping specialist who can take this plant’s colorful assets to the next level.