Planaria in a shrimp tank: how to identify and get rid of them
Small white or brown worms gliding across the glass are one of the most common surprises in a shrimp tank. Some of them are harmless, and some are planaria, flatworms that many shrimp keepers want gone, especially in breeding tanks. Below is how to tell them apart, why they show up, what risk they pose, and the removal methods keepers most often report working. This is a summary of hobby references and owner reports, not the result of our own trials.
How to identify planaria
Planaria are flatworms, usually a few millimeters to about a centimeter long. Look for these signs, ideally with a flashlight or a magnifying glass:
- A triangular or arrow-shaped head. Many species have a spade-shaped head, sometimes with two small "ear" flaps.
- Two dark eye spots that can look a little cross-eyed.
- Smooth gliding. Planaria slide along surfaces like a tiny slug. They don't wiggle or whip.
- A flat body that's white, cream, brown or gray.
| Worm | What it looks like | Harm to shrimp |
|---|---|---|
| Planaria (flatworm) | Flat, arrow-shaped head, eye spots, glides smoothly | Commonly reported to prey on shrimplets, eggs and weak or molting shrimp |
| Detritus worms | Thin, thread-like, wiggle and whip, often in the substrate | Generally considered harmless scavengers |
| Nematodes | Very thin, clear, thrash in an S shape | Generally considered harmless |
| Rhabdocoela | Tiny, fast, rounded front with no clear head shape | Generally considered harmless |
If the worms wiggle, they're very unlikely to be planaria. The head shape and smooth gliding are the giveaways.
Are planaria dangerous to shrimp?
Owner reports and hobby references commonly describe planaria preying on shrimplets and eggs, and sometimes attacking shrimp that are weak or freshly molted. A few planaria in a big, established colony may never cause visible losses, but in a breeding tank a population boom can be a real problem. If your colony isn't growing despite berried females, planaria are one possible cause; see why cherry shrimp aren't breeding for the others.
Why planaria appear
- Hitchhikers. They usually arrive on plants, moss, hardscape or in water from another tank. That's one reason not to pour bag water into your tank when you acclimate new shrimp.
- Overfeeding. A few planaria can live unnoticed. Extra food is what usually lets the population explode. Our shrimp food guide covers how much to feed.
- Leftover protein foods. High-protein foods left overnight are frequently linked to booms in owner threads.
How to get rid of planaria, from gentlest to strongest
- Cut feeding back. Feed less, remove leftovers within a few hours, and vacuum mulm from open areas. This alone often shrinks the population over a few weeks, and it's the step that keeps them from coming back.
- Trap them. A planaria trap baited with a small piece of protein food overnight can pull out large numbers. Empty and rinse it each morning. Traps reduce numbers but rarely wipe out a population on their own.
- Remove them by hand. Wipe them off the glass with a paper towel or siphon them out during water changes.
- Use a shrimp-safe planaria treatment. Products based on betel nut extract, such as No Planaria, are widely used by shrimp keepers and are generally described as shrimp-safe when used as directed. Two cautions come up again and again: they typically kill snails too, and the dead worms need removing because they can foul the water. Follow the label exactly and do a large water change afterward.
- Fenbendazole (last resort). Some keepers use fenbendazole-based dewormers. It's commonly reported to kill snails as well, and it's not made for aquariums, so many keepers try the options above first.
After treatment
Keep feeding light, keep an eye on the glass at night with a flashlight, and keep testing so a die-off doesn't cause an ammonia spike. Our test kit guide covers what to measure. Quarantining or rinsing new plants before they go in is the main way keepers prevent a repeat. If you're also seeing tiny tentacled polyps, read our guide to hydra in a shrimp tank, since the same treatments often handle both.
FAQ
Are planaria harmful to shrimp?
They are commonly reported to prey on shrimplets, eggs and weak or freshly molted shrimp. A few in a large colony may not cause visible losses, but a boom in a breeding tank can.
How do I tell planaria from detritus worms?
Planaria have a flat, arrow-shaped head with two eye spots and glide smoothly. Detritus worms are thin and thread-like and wiggle or whip.
What causes planaria in a shrimp tank?
They usually arrive on plants, moss or in water from another tank, and overfeeding is what typically lets the population explode.
Is No Planaria safe for shrimp?
Betel-nut-based treatments are widely described as shrimp-safe when used exactly as directed, but they typically kill snails, and dead worms should be removed with a water change afterward.
Do planaria traps work?
Traps baited with protein food can remove many planaria overnight, but they rarely eliminate a population alone. They work best combined with lighter feeding.
Will planaria go away on their own?
Their numbers often shrink when feeding is cut back and leftovers are removed, though a few may remain at low levels.
Our take
Most white worms in shrimp tanks are harmless, so identify before you treat. If you do have planaria, feeding less is the cheapest and most lasting fix, traps help with numbers, and a shrimp-safe treatment is there for stubborn cases, with the trade-off that snails usually don't survive it.
Sources: owner discussions on r/shrimptank and r/Aquariums (2024–2026); manufacturer instructions for betel-nut-based planaria treatments and planaria traps; Google search suggestions for "planaria in shrimp tank" and "how to get rid of planaria." Checked October 2026.