Mechanical and asphyxic rot of the stem or rhizome commonly occurs due to human error during planting, not nutritional deficiencies. When rosette or rhizomatous plants (like Anubias, Microsorum, Bucephalandra) are planted too deeply, burying the 'crown' or rhizome in the sand or soil, the soft tissues drown and rot. In stem plants (Rotala, Ludwigia), planting too many stems bunched together in a single hole deprives the lower portions of light and oxygen, causing them to blacken and snap.

For epiphytes and rosettes: seemingly healthy, green leaves detach and float upwards with a black, mushy base. The rhizome turns into foul-smelling mush. For stem plants: the lower part of the plant blackens, becomes stringy, and breaks off, unmooring the entire plant from the substrate and causing it to float to the surface ('floating stem').

Burying the rhizome under the substrate. For Anubias and Microsorum, the rhizome MUST strictly remain exposed to the water column. Planting in dense, tied bunches (as they are sold in shops with rockwool and lead weights) without first separating individual stems with tweezers. Excessive compression of the substrate around the soft stem.

Immediately remove the plant from the substrate. With sharp scissors, completely cut away the black rotting part of the rhizome or stem until reaching firm, living white/green tissue. Rot spreads very quickly like a necrotic infection. Replant healthy stems individually, leaving a few millimeters of space between them for light and water flow penetration.

When buying a pot of stem plants, remove all the rockwool, patiently separate every single stem, and plant it with curved tweezers, spacing them about 1 cm apart ('mosaic method'). Rhizomatous plants (Anubias, Ferns) should be tied to rocks or driftwood using fishing line or cyanoacrylate gel glue, ensuring the rhizome runs free above the substrate.