Quick answer: Anubias rot often looks contagious. Many keepers lose one Anubias after another in the same tank over a few days or weeks, but no one has confirmed what causes it, so nobody can say for sure how it spreads. The safe approach is to treat it as contagious: take the plant out, cut the rhizome back into firm, healthy tissue with a margin, sterilise your scissors, and check your other Anubias every week. The mistake most people make is watching the yellow leaves. Rot starts in the rhizome, so that is where you need to look.
Anubias is sold as the plant you cannot kill. Low light, no CO2, tie it to a rock and forget about it. Then one day a leaf comes away in your hand with no resistance at all, and the rhizome underneath is soft and dark.
That is rhizome rot, and the next question everyone asks is whether the rest of their Anubias are about to go the same way. Below is what is actually known, what is just repeated online, and what I did when one of my own plants got it.
Anubias rot at a glance
| Detail | What we know |
|---|---|
| Where it starts | The rhizome (the thick horizontal stem), not the leaves |
| Main sign | Soft, dark or mushy rhizome; leaves fall off with almost no pull |
| Confirmed cause | None. Bacterial or fungal infection are the leading theories |
| Contagious? | Not proven, but keepers often report it spreading between Anubias |
| Best treatment | Cut away all soft tissue with a margin of healthy rhizome |
| Chemical dips | Hydrogen peroxide, potassium permanganate and bleach are widely reported as not reliable |
| Most common avoidable cause | A buried rhizome |
| Sign of recovery | New leaves growing from the remaining rhizome |
What Anubias rhizome rot looks like
The rhizome is the thick horizontal stem the leaves and roots grow from. On a healthy Anubias it is firm, pale to mid green, and sits above the substrate, attached to wood or rock.
Rot starts there, not in the leaves. That is the most useful thing to know, because most people look at a yellowing leaf and miss what is happening underneath it.
Early stage. A soft patch appears on the rhizome, usually darker than the tissue around it. Press it gently and it gives, while the rest of the rhizome does not. Leaves growing from that section start to yellow and detach with very little pull.
Late stage. The soft section turns dark brown or black and goes mushy. The rhizome can break apart when you lift the plant, and leaves come off on their own and float around the tank. Some keepers also notice a bad smell when they cut into it.
The tell. Texture is what separates rot from everything else. Nutrient problems and low light change the colour of the leaves, but the rhizome stays firm. With rot, the rhizome itself fails.
Is Anubias rot contagious?
Sources disagree on this, so here is the honest position rather than the answer that sounds most confident.
What keepers report. On forums the pattern is remarkably consistent. People describe losing one Anubias after another, sometimes roughly one plant every few days, in tanks where everything else looked fine. Different people in different tanks describe the same pattern again and again.
What is actually established. Not much. Aquarium Co-Op, which has sold thousands of Anubias, says researchers have not found a definitive cause, and the working theories are bacterial or fungal infection, possibly attacking plants that were already weakened. If the cause is not confirmed, then strictly speaking neither is the way it spreads.
How I would put it. The pattern strongly suggests something that passes between plants in the same water, but it has not been formally identified. Treating it as contagious costs you very little and protects you if it is, so that is what I did.
Rot vs melt vs deficiency: which one do you have?
Plenty of Anubias problems look alarming but are not rot. Feel the rhizome before you do anything else.
| What you see | Rhizome | Likely cause | What to do |
|---|---|---|---|
| Rhizome soft or mushy, leaves fall off | Soft, dark | Rhizome rot | Isolate and cut back now |
| Leaves soft or see-through, plant recently added | Firm | New plant melt | Leave it alone |
| Leaves pale or yellow, plant otherwise solid | Firm | Nutrient deficiency | Dose liquid fertiliser, judge by new growth |
| One old leaf yellowing, new growth healthy | Firm | Normal ageing | Nothing |
| Dark green spots or film on leaves | Firm | Green spot algae | Wipe leaves, check light hours |
The honest part most guides leave out: a firm rhizome rules out rot almost every time. A newly added Anubias dropping a couple of leaves is usually just aquarium plant melt while it adjusts to life underwater. Pale leaves on a solid plant point to a deficiency, which shows up slowly in a plant this slow-growing. Our plant deficiency symptoms guide helps you narrow down which nutrient is missing.
What causes Anubias rot?
Nobody knows for certain, and any page telling you otherwise is more confident than the evidence allows. These are the theories you will come across:
Bacterial or fungal infection. The most commonly cited theory, and the one that best fits the spreading pattern. A weakened plant may be more open to it.
Damage during shipping or planting. A bruised, crushed or cut rhizome gives something an easy way in.
Burying the rhizome. A rhizome pushed into the substrate rots reliably. That is not a mystery disease, it is a planting mistake, and it may be behind a fair share of cases blamed on infection.
Poor or unstable water. Often mentioned, rarely shown to be the direct cause. Anubias rot appears in well-kept tanks with good parameters too.
Check for a buried rhizome first. It is the only cause on this list you can rule in or out just by looking, and if any part of the rhizome is under the substrate, that is very likely your answer.
What I did when my Anubias got rot
When one of my Anubias developed rot, I took it out of the display tank and kept it on its own instead of leaving it with the others. Then I cut the rotten section of rhizome away and left the plant to recover.
Separating it first is the part I would repeat. If rot does spread between plants, leaving an affected one in the tank while you decide what to do is the one thing you clearly should not do. And if it turns out not to spread, isolating it cost you nothing.
None of my other Anubias got it. They stayed healthy the whole time.
I want to be careful about what that does and does not prove. One plant in one tank is a single case, not evidence. I cannot separate the two explanations either: pulling it out may have stopped the spread, or it may never have been going to spread in my tank. What I can say is that isolating and cutting is cheap, fast and low risk, and in my case nothing else was lost.
The cut plant is still going. It has not been long enough to call it a recovery, and I would rather say that than claim one I have not seen yet. I will update this section when I know.
How to treat Anubias rot, step by step
- Take the plant out. Lift it clear of the tank rather than treating it in place. If it is tied or glued to wood, take the wood out with it.
- Find where the firm tissue starts. Run your fingers along the rhizome and feel for the boundary between soft and solid.
- Cut well past that boundary. Do not cut right at the edge of the damage. Go into clean, firm tissue with some margin, because the visible rot and the real extent are not always the same. Losing an extra centimetre (about half an inch) of healthy rhizome is far better than leaving infected tissue behind.
- Throw the rotten section away. Not into another tank, and not into a quarantine tank with other plants.
- Sterilise your scissors before touching anything else. This is the step people skip. If rot is transmissible at all, your own tools are the most obvious way to carry it from plant to plant.
- Keep the cut plant separate for a few weeks if you can. New leaves from the remaining rhizome are the sign you cut far enough.
- Check your other Anubias weekly. Run a finger along each rhizome looking for soft spots, and keep doing it for a while rather than checking once.
A note on hydrogen peroxide dips. They come up constantly on forums. Some keepers swear by them, but many report no difference, and Aquarium Co-Op reports that peroxide, potassium permanganate, bleach and even weeks of antibiotic or antifungal treatment did not heal affected plants. Since the cause itself is unconfirmed, I would not count on a dip. Cutting away the damaged tissue is the one step most experienced keepers agree on.
How to prevent Anubias rot
Never bury the rhizome. Attach Anubias to wood, rock or a decoration. If you plant it in the substrate, only the roots go under. The same rule applies to Java fern and Bucephalandra, and ignoring it is the most common way people kill plants that are otherwise very hard to kill.
Buy tissue-culture plants when you can. Plants grown in sterile cups start clean, and some growers believe this is the most reliable way to avoid rot, because potted farm plants can arrive already carrying it.
Quarantine new plants if you have had rot before. A couple of weeks in a separate container is not practical for everyone, but it is worth it once you have lost plants.
Handle new plants gently. Avoid crushing the rhizome when you attach it. A dab of gel superglue on the underside, or loose cotton thread, is kinder than tying it tight with fishing line.
Feed the leaves, not the substrate. Anubias takes most of its nutrients from the water through its leaves, so a little liquid fertiliser helps more than root tabs. Save the tabs for crypts and swords.
Keep some flow around it. Anubias in a completely still corner, with detritus building up around the rhizome, seems to fare worse. That is a pattern keepers notice rather than a proven cause, but gentle flow is easy to provide.
Common mistakes with Anubias rot
Waiting to see if it improves. It does not. Every day you wait, more rhizome is lost, and if it spreads, your other plants are exposed for longer.
Cutting right at the edge of the rot. The damage usually runs further than it looks, so always cut with a margin.
Using the same scissors straight away. Sterilise them before you trim anything else.
Moving the plant into another tank to recover. You may just be moving the problem to a second tank.
Blaming your water. Anubias rot shows up in well-maintained tanks with good parameters. Chasing numbers can distract you from the plant that actually needs cutting.
If you are replacing lost plants, our list of low light aquarium plants covers other hardy options that do well without CO2, including Java moss and flame moss.
FAQ
Is Anubias rot contagious?
Keepers consistently report it spreading between Anubias in the same tank, but the cause has never been confirmed. That makes it a strong observed pattern rather than established science, so treating it as contagious is the safer approach.
Can Anubias recover from rhizome rot?
Yes, if enough firm rhizome is left after you cut the damage away. New leaves from the remaining section confirm it is recovering. If the whole rhizome has gone soft, the plant is usually lost.
Will Anubias rot spread to Java fern or Bucephalandra?
Reports of spreading are almost all between Anubias plants. Because the cause is still unknown, though, nobody can rule other rhizome plants out with confidence, so check them too.
How fast does Anubias rot spread?
Keepers describe losing plants over days to weeks rather than months. That is why acting quickly matters more with rot than with most plant problems.
Does hydrogen peroxide cure Anubias rot?
There is no good evidence that it does. Many keepers report that peroxide and other chemical dips make no difference, and cutting away the soft tissue remains the most reliable treatment.
Should I tear down my tank if I find Anubias rot?
No. Remove the affected plant, cut it back, sterilise your tools and keep an eye on your other Anubias. There is no evidence that a full tank reset is needed.
How do I tell Anubias rot from melting?
Feel the rhizome. A firm rhizome with some leaf loss means melt or normal shedding, while a soft or mushy rhizome means rot.
Final word
Check the rhizome, not the leaves. That is the whole diagnosis in one line.
If it is soft, cut back into clean tissue with a margin, sterilise your scissors and keep watching your other Anubias. The cause is still unsettled, and anyone who claims to know exactly what it is has gone further than the evidence. The practical response is the same either way, and acting as though it spreads costs you very little.
0 Comments