By Hektor Jorgo
Anubias has a reputation as one of the most indestructible aquarium plants — it tolerates low light, gets eaten by almost nothing, and survives conditions that would kill more demanding plants. So when an anubias starts dying, it's often confusing, because the usual culprits (light, water quality, algae) don't always seem to fit. In the large majority of cases, the answer is simpler than it seems: the rhizome — the thick, horizontal stem the leaves and roots grow from — has been buried, and it's rotting.
Direct Answer: Almost Always a Buried Rhizome
Anubias is an epiphyte: in the wild, it grows attached to rocks and driftwood along riverbanks, with its rhizome exposed to water and air, not buried in soil. When anubias is planted the way many other aquarium plants are — rhizome pushed into the substrate — the rhizome is deprived of oxygen and sits in a more anaerobic environment, which favors the bacteria and fungi responsible for rot. Over time, the buried portion softens, discolors, and can develop a foul smell, and the rot can spread along the rhizome if not addressed.
The fix for both treating and preventing this is the same: the rhizome needs to be exposed to water, not buried — attached to driftwood, rock, or simply resting on top of the substrate where roots can spread into it without the rhizome itself being covered.
Recognizing Rot vs. Normal Aging
It's worth distinguishing rot from normal anubias behavior, since anubias is naturally slow-growing and can look a bit "static" even when healthy:
- Normal: Individual older leaves yellowing and dying back one at a time while the rhizome stays firm and new leaves continue emerging — this is just normal leaf turnover.
- Rot: The rhizome itself — the thick horizontal stem — becomes soft, mushy, and discolored (brown, black, or translucent), often with multiple leaves yellowing or detaching around the same area, and sometimes a foul smell when the affected section is touched or removed.
If only individual leaves are affected and the rhizome feels firm throughout, that's more likely normal aging or a leaf-specific issue (algae buildup, physical damage) than rot.
What Causes It Beyond Burial
While burial is the leading cause, a few other factors can contribute to or accelerate rot:
- Poor water flow around the rhizome — stagnant areas favor the anaerobic conditions rot-causing organisms prefer, similar to the dead-spot conditions covered in our Calothrix algae guide.
- Heavy algae buildup on the rhizome and leaves, which can smother the plant's surface and trap organic debris against it — see our general algae guide for what drives algae growth in the first place.
- Physical damage to the rhizome (from handling, decor shifting, or aggressive fish/snails) creating an entry point for rot-causing organisms.
Java fern, another common epiphyte, deals with its own version of leaf-surface algae buildup rather than rhizome rot — our java fern algae guide covers how that compares. And because anubias's rhizome doesn't feed from substrate the way root-feeding plants do, substrate choice (covered in our substrate guide) matters far less here than it does for plants like Amazon swords.
Treatment: Trimming and Remounting
- Remove the plant and inspect the full rhizome — soft, discolored sections won't recover and need to be cut away.
- Cut into healthy tissue — use clean scissors or a blade, cutting a short distance past where rot appears to end, into rhizome that feels firm.
- Remount correctly — tie or glue the rhizome to driftwood or rock with the rhizome itself exposed to water flow, or rest it on top of substrate without burying it. Cotton thread, fishing line, or aquarium-safe glue all work; roots will eventually anchor the plant on their own.
- Address contributing factors — if flow was poor or algae was heavy in that area, those are worth fixing too, so the same conditions don't cause a recurrence.
Quick Reference
- Anubias rhizome rot is almost always caused by burying the rhizome in substrate
- Healthy rhizome should be exposed — mounted on driftwood/rock or resting on top of substrate
- Soft, mushy, discolored, or foul-smelling rhizome tissue = rot, not normal aging
- Trim away affected tissue, cutting into firm healthy rhizome
- Remount with the rhizome exposed to prevent recurrence
- Poor flow and heavy algae can contribute — address both if present
- Anubias usually recovers well if rot is caught before it spreads through the whole rhizome
