Ludwigia Repens Care Guide: Grow Red Leaves Without CO2
Ludwigia repens is a beginner-friendly stem plant that adds red color to planted tanks without CO2. Learn about light, substrate, propagation, and melt.
If you just set up your first planted tank and you're staring at a bare-looking background, Ludwigia repens is one of the easiest ways to add color without buying a CO2 system. It's a stem plant that turns from green to red under decent light, and it forgives beginner mistakes better than most red plants do. This guide covers exactly what a low-budget, no-CO2 planted tank needs to know before buying it.
Quick Answer: Ludwigia repens is a beginner-friendly stem plant that grows 6-20 inches tall, tolerates a wide pH range of 5.0-8.0, and does not require CO2 injection — though CO2 and medium-high light will make its leaves turn a deeper red. It thrives in temperatures of 68-84°F (20-28°C) and works well as a midground or background plant in most freshwater community tanks.
What Is Ludwigia Repens?
Ludwigia repens is a stem plant native to the southeastern United States and parts of Central America. It belongs to the evening primrose family, Onagraceae, and grows both underwater and above the waterline.
Its oval leaves are green on top and reddish underneath in low light. Under stronger light, the whole leaf can flush deep red or copper. This color range is exactly why beginners pick it over trickier red plants like Rotala.
Quick facts:
- Height: 6-20 inches, depending on light and trimming
- Growth rate: Moderate to fast
- Difficulty: Easy — good first "red" plant
- Placement: Midground or background
- Light: Low to high (best color at medium-high)
Pro Tip: If you're on a tight budget and don't want to buy a CO2 kit yet, start with regular Ludwigia repens instead of the 'Rubin' variety. It colors up decently under just a standard LED light.
Does Ludwigia Repens Need CO2?
No, Ludwigia repens does not need CO2 injection to survive. It grows fine in a low-tech tank with just fish waste and root nutrients as fertilizer.
That said, CO2 changes what the plant looks like. Without it, leaves usually stay more green with reddish undersides. With injected CO2 and stronger light, the whole leaf can turn bright red or orange, and growth speeds up noticeably.
Aquatic plants pull carbon and nutrients directly from the water column to fuel photosynthesis, and adding CO2 simply removes one of the plant's growth bottlenecks [1]. That's why the color change is so predictable once CO2 is added.
Common Myth: "Red aquarium plants always need pressurized CO2 to survive." Reality: Ludwigia repens can live for years in a CO2-free tank — it just won't reach its deepest red color without extra carbon and stronger light.
If a low-tech, no-CO2 setup fits your budget better, a nutrient-rich substrate can make up some of the difference. Products like Fluval Stratum give root feeders like Ludwigia a steady nutrient supply without any gear beyond the tank itself.
Substrate, Root Tabs, and Nutrients
Ludwigia repens feeds through its roots more than most stem plants, so substrate choice matters. It will grow in plain gravel, but it grows noticeably faster and fuller in nutrient-rich substrate.
If your tank already has plain gravel or sand, root tabs are the cheapest fix. Push one near the base of each plant cluster every 4-6 weeks.
- Nutrient-rich substrate (best long-term option): feeds roots continuously
- Root tabs in plain gravel (budget option): cheap, works in existing tanks
- Liquid fertilizer alone (least effective for this plant): Ludwigia relies more on roots than leaves for nutrient uptake
Pro Tip: New to planted tanks and don't want to re-substrate your whole tank? A few Seachem Flourish root tabs tucked under the roots of your Ludwigia will do most of the job for a few dollars a month.
Iron deficiency is one of the most common reasons new leaves come in pale or yellow instead of red. Dosing a liquid iron supplement alongside root tabs usually fixes this within one to two weeks.
Light Needs for the Best Red Color
Ludwigia repens needs medium to high light to turn deeply red — low light keeps it mostly green. This is the single biggest factor budget-conscious keepers overlook when the plant "won't turn red."
A basic low-output LED will keep the plant alive and green. To get real red or orange coloring, aim for a fixture in the medium-high PAR range, roughly comparable to a mid-tier planted-tank LED running 8-9 hours a day.
| Light Level | Typical Result | Best For |
|---|---|---|
| Low light | Green leaves, slow growth | Budget no-CO2 tanks, beginners |
| Medium light | Green with red undersides | Most community tanks |
| High light + CO2 | Deep red/orange leaves | Aquascapers chasing color |
Recommendation: For a first planted tank on a budget, medium light without CO2 is the sweet spot — decent color, low risk of algae.
Pro Tip: If your budget only stretches to one light upgrade, a Nicrew ClassicLED planted tank light is enough to push Ludwigia toward red without needing CO2 at all.
Water Parameters and Tank Compatibility
Ludwigia repens tolerates a wide range of water conditions, which is why it survives so many beginner setups. It handles temperatures of 68-84°F (20-28°C) and a pH between 5.0 and 8.0.
This flexibility makes it compatible with most common community fish, including tetras, rasboras, and livebearers. It also holds up well in slightly harder water, unlike more sensitive plants such as certain Rotala species.
Water quality still matters for overall tank health, since stable parameters reduce stress on both plants and fish [2]. A weekly water change of 20-30% keeps nutrient levels balanced and algae in check.
Because Ludwigia repens grows quickly, it also absorbs excess nitrate produced by fish waste. Fast-growing stem plants are commonly used to help offset the nitrogen load in stocked community tanks [3], which makes this plant a practical choice, not just a decorative one.
Planting and Propagation: How to Trim and Replant
Ludwigia repens is one of the easiest aquarium plants to propagate — you just cut and replant stems. This makes it a good "free plant" source once your original cluster settles in.
To propagate it:
- Let the main stem grow to at least 4-6 inches
- Cut a healthy top section with a few leaf nodes
- Strip the bottom inch of leaves from the cutting
- Push the stripped end into the substrate
- Roots typically form within 1-2 weeks
Pro Tip: Trim the tops regularly instead of letting stems reach the surface. Regular trimming keeps the plant bushy and stops it from shading out lower-light plants nearby.
A pair of curved aquascaping scissors makes clean cuts near the substrate line, which reduces stem rot compared to tearing plants by hand.
Growing Ludwigia Repens Emersed (Out of Water)
Yes, Ludwigia repens can grow completely out of water, and many nursery-grown plants are raised this way. Growers often produce it emersed because it's cheaper and faster than growing it submerged.
This matters for new buyers because emersed-grown Ludwigia often "melts" — loses its older leaves — after being planted underwater. This is a normal transition, not a sign of a dying plant.
The plant is switching from emersed leaf structure to submerged leaf structure, a process called heterophylly in aquatic plants. New, water-adapted leaves usually appear within 1-3 weeks even as old leaves die back.
Common Myth: "If my new Ludwigia is losing leaves, I did something wrong." Reality: Melting after planting is expected for emersed-grown stock and does not mean the plant is dying, as long as new growth appears within a few weeks.
Setting this up for the first time? Our full beginner's guide to low-tech planted tanks covers exactly how to plant stems without disturbing new roots.
Ludwigia Repens vs Ludwigia Repens 'Rubin'
The standard Ludwigia repens and the 'Rubin' cultivar look similar but need different light levels to show red color. Rubin is a selectively bred variant with a stronger red pigment.
| Feature | Ludwigia repens | Ludwigia repens 'Rubin' |
|---|---|---|
| Base color | Green, reddish underside | Deep red, even in lower light |
| Light needed for red | Medium-high | Low-medium |
| Beginner friendliness | Very easy | Easy |
| Typical price | Lower | Slightly higher |
| Recommendation | Best for budget/low-tech tanks | Best if red color is the priority |
For a first-timer prioritizing an easy, forgiving plant, standard Ludwigia repens is the safer starting pick.
Common Mistakes New Growers Make
Most Ludwigia repens problems come from planting too deep or expecting instant red color. These mistakes are easy to avoid once you know what to look for.
- Burying stems too deep: only the bottom inch should be in the substrate — deeper planting causes stem rot
- Expecting red color under low light: without medium-high light, the plant will simply stay green
- Not trimming: leggy, unpruned stems block light to everything below them
- Skipping root tabs in plain gravel: without nutrients, growth stalls after the first few weeks
- Panicking during melt: removing a newly planted stem too early interrupts the adjustment period
Need to keep costs down while fixing these issues? See our budget-friendly planted tank gear picks before buying a full CO2 setup.
Conclusion
Ludwigia repens is one of the most forgiving red-leaning plants for a first planted tank, and as of August 2026, it remains a top beginner recommendation among low-tech aquascapers. It survives a wide pH and temperature range, propagates for free, and doesn't require CO2 to stay alive. For the best color, prioritize medium-high light and root nutrition over anything else.
Ready to bring color to your first planted tank? Start with a single bunch of Ludwigia repens, a root tab, and patience through the first few weeks of melt.
