Planaria in Aquarium: How to Identify and Remove Them Safely
Published: 2026-10-29 · FishyKart Blog
Planaria are small, flat freshwater flatworms, usually about 5-15 mm long, with a triangular, arrow-shaped head and two dark eyespots that look like crossed eyes. They glide smoothly over the glass and appear in large numbers when there is too much leftover food. They rarely hurt adult fish, but in shrimp tanks they can attack baby shrimp, eggs and moulting adults, so most shrimp keepers remove them.
Photo: Karlajolote - Wikimedia Commons, CC BY-SA 4.0
Planaria or Something Else?
| Worm | How to recognize it |
| Planaria | Flat, triangular head with two eyespots, glides smoothly; white, brown or black |
| Detritus worms | Very thin, round, white, wriggle and whip, often in gravel; harmless |
| Nematodes | Tiny, thread-like, thrash in a C or S shape; usually harmless in small numbers |
| Leeches | Flat but with suckers at both ends, move like an inchworm |
Small white worms on the glass in a new tank are often detritus worms or nematodes, not planaria. Look closely with a magnifying glass or a phone camera on zoom for the head shape.
Why Planaria Appear
The main cause is excess food. Leftover pellets, wafers and frozen food feed the worms, and the population grows fast. Rich substrate and lots of debris also help. Planaria usually arrive on new plants, java moss or gravel from another tank.
How to Remove Planaria
- Feed less: give only what the animals finish in a few minutes and remove leftovers. This alone shrinks the population.
- Clean up: vacuum the substrate and wipe the glass during water changes.
- Trap them: a planaria trap or a small jar with a piece of meat or fish food left overnight collects many worms. Empty it each morning, away from the tank.
- Manual removal: suck worms off the glass with a pipette or turkey baster. Never crush or cut them in the tank.
- Fish that eat them: many small fish will pick off planaria, but most fish also eat baby shrimp, so this is not an option for breeding shrimp tanks.
Shrimp-Safe Treatment
If cleaning and traps are not enough, shrimp keepers commonly use fenbendazole or products based on betel nut extract, dosed exactly as the label says. These are generally tolerated by cherry shrimp and other dwarf shrimp, but they kill snails, including nerite snails and ramshorn snails, so move snails out first. Dead worms rot quickly, so remove what you can, increase aeration and do a partial water change after treatment. Fenbendazole also kills hydra.
Mistakes to Avoid
- Treating harmless detritus worms as planaria.
- Dosing medicine while continuing to overfeed. Without less food they come back.
- Forgetting the snails and other invertebrates before treatment.
- Overdosing in a small tank: in 5 gallons (19 liters), small measuring errors matter a lot.