Planaria infestation

The body is flat and unsegmented with continuous gliding movement; many triclads have a widened head and two eyespots, but this is not universal. They often emerge after dark or during feeding and gather beneath décor and in substrate. Observed predation, missing eggs and weakened shrimp matter more than presence alone.

Freshwater planarians are free-living flatworms that glide over glass and décor. Some are predators or scavengers and, at high density, may threaten eggs, tiny invertebrates or freshly moulted animals; other similar worms are harmless. ‘White worm’ is therefore not a diagnosis: risk must be tied to shape, behaviour and host population.

Uneaten protein food, carcasses and detritus support growth; plants, décor and animals can introduce them. A tank without predators and with many refuges may make them suddenly conspicuous. Presence does not prove absolute poor hygiene, but rapid growth indicates available resources or recent introduction.

Escalate with observed predation, reduced hatch, wounds on small invertebrates or rapid growth despite food correction. Worms emerging from within a fish or protruding from the vent are not free-living planarians and require veterinary diagnosis. Preserve live specimens for identification.

Rhabdocoels and other tiny turbellarians often have rounded heads and may be harmless; detritus worms are cylindrical or segmented, while leeches use suckers. Nematodes swim with serpentine motion rather than gliding as a flat sheet. Viewing an isolated specimen prevents indiscriminate control.

Use a baited trap overnight to estimate density and collect specimens without dismantling the tank. Photograph from above and the side with scale, noting head, eyes, gut branching and movement. Where valuable breeding stock is at risk, microscopy or specialist identification is preferable to silhouette alone.

Use a baited trap overnight to estimate density and collect specimens without dismantling the tank. Photograph from above and the side with scale, noting head, eyes, gut branching and movement. Where valuable breeding stock is at risk, microscopy or specialist identification is preferable to silhouette alone.

Reduce excess food, remove carcasses and siphon concentration points. Traps allow gradual, measurable reduction; inspect removable plants and materials outside the tank. Do not deliberately crush or fragment worms in the aquarium, and do not use products before checking safety for shrimp, snails and biofilter.

Control combines resource reduction, repeated trapping and quarantine of introductions. Any flatworm-active product requires identification, a local label and a plan for residues and sensitive invertebrates; mass die-off can worsen water quality. Judge results through repeated night counts, not a single day without sightings.

Quarantine plants and décor according to risk, avoid transferring water and detritus between tanks, and feed consumable amounts. Regularly inspect dark zones and beneath feeding dishes. A population found early is easier to assess and contain.

Escalate with observed predation, reduced hatch, wounds on small invertebrates or rapid growth despite food correction. Worms emerging from within a fish or protruding from the vent are not free-living planarians and require veterinary diagnosis. Preserve live specimens for identification.