How to Treat Planaria in a Shrimp Tank Safely

Finding planaria in a shrimp tank is every shrimp keeper’s nightmare. These small, flat worms are not just unsightly — they actively prey on shrimp eggs and shrimplets, and can decimate a breeding colony if left unchecked. The challenge is eliminating them without harming the shrimp you are trying to protect.

At Gensou, we have dealt with planaria outbreaks in our own systems and helped countless Singapore hobbyists through the treatment process over our 20-plus years in the trade. This guide walks you through the safest, most effective methods to rid your shrimp tank of planaria.

Identifying Planaria

Before treating, confirm that you actually have planaria and not a harmless look-alike. Planaria are flatworms (class Turbellaria) that are easily confused with other common tank worms.

Feature	Planaria	Detritus Worms	Rhabdocoela
Shape	Flat, arrow-shaped head	Round, thread-like	Small, round-headed
Size	5–15 mm	1–10 mm	1–3 mm
Movement	Glides smoothly on surfaces	Wiggles in water column	Glides, but smaller
Head	Distinct triangular/arrow head with eyespots	No distinct head	Round, no distinct head
Danger to shrimp	Yes — predatory	No — harmless scavengers	No — harmless

The key identifier is the arrow-shaped or triangular head with two visible eyespots (dark dots). If you see a flatworm with this characteristic head shape gliding across the glass, especially at night, you have planaria.

Detritus worms (Annelida) are thin, round, and wriggle through the water — they are harmless and a sign of excess organic matter, not a threat to shrimp. Rhabdocoela are tiny, round-headed flatworms that are also harmless. Only planaria warrant treatment.

Why Planaria Are Dangerous to Shrimp

Planaria are predators. In a shrimp tank, they pose several specific threats:

Egg predation — planaria actively seek out and consume shrimp eggs, reducing or eliminating successful breeding.
Shrimplet predation — newly hatched shrimplets (1–3 mm) are vulnerable to planaria attack, particularly at night when the worms are most active.
Weak/moulting shrimp — freshly moulted shrimp are soft and vulnerable; planaria have been observed feeding on weakened or moulting shrimp.
Population explosion — planaria reproduce rapidly, especially when there is excess food. A few worms can become hundreds within weeks in a warm Singapore tank (28–32 °C).

If you notice your shrimp colony is not producing babies despite having berried (egg-carrying) females, planaria predation on eggs and shrimplets may be the cause. Night-time observation with a torch often reveals the extent of the problem, as planaria are predominantly nocturnal.

Safe Treatments for Shrimp Tanks

Two main chemical treatments are considered shrimp-safe when dosed correctly:

No Planaria (Betel Nut Powder)

No Planaria is a commercial product made from betel nut extract (areca nut). It is specifically formulated to kill planaria, hydra and other flatworms without harming shrimp, snails or fish at recommended doses.

Active ingredient: Areca nut extract
Dosage: Typically 1 scoop (included) per 50 litres, but always follow the specific product’s instructions
Shrimp safety: Safe at recommended dose; shrimp may be slightly less active during treatment but recover fully
Snail safety: Generally safe, though some hobbyists report snail stress at higher doses; dose conservatively if you have valuable snails
Availability: Widely available in Singapore aquarium shops and online

Fenbendazole

Fenbendazole is an anthelmintic (deworming) drug used in veterinary medicine. It is effective against planaria and is shrimp-safe when dosed carefully.

Source: Available as Panacur or generic fenbendazole powder from veterinary suppliers; also sold as Safeguard canine dewormer (222 mg/g granules)
Dosage: 0.1 g per 100 litres of pure fenbendazole. If using Safeguard granules (22.2% fenbendazole), use approximately 0.45 g per 100 litres
Shrimp safety: Safe at recommended dose; slight overdose is tolerated but avoid excessive dosing
Snail safety: Lethal to snails at treatment doses. If you keep snails, remove them before treatment
Note: Does not dissolve easily in water; pre-mix in warm dechlorinated water and stir vigorously

Important: Fenbendazole will kill snails. If you keep Nerite, Mystery or other snails alongside your shrimp, either remove the snails before treatment or use No Planaria instead, which is generally safer for snails at recommended doses.

Step-by-Step Treatment Protocol

This protocol applies to both No Planaria and fenbendazole treatments. Follow each step carefully.

Day 0: Preparation

Perform a 20% water change with dechlorinated water (PUB water treated with a conditioner to neutralise chloramine).
Remove activated carbon and any chemical filtration media from your filter — these will adsorb the medication and reduce its effectiveness.
Note your exact water volume (account for substrate, hardscape and equipment displacement).
If using fenbendazole, remove all snails to a separate container.
Turn off UV sterilisers if running.

Day 0: First Dose

Calculate your dose based on actual water volume.
For No Planaria: dissolve the powder in a cup of tank water and distribute evenly across the tank surface.
For fenbendazole: pre-dissolve in warm dechlorinated water (it does not dissolve easily — stir or shake vigorously), then add to the tank.
Increase surface agitation slightly to maintain oxygen levels, as dead planaria decomposing can reduce oxygen.

Day 1–2: Observation

Dead planaria will appear as white, curled-up worms on the substrate and glass. This is normal and expected.
Shrimp should remain active. Slight reduction in activity is normal but they should still move and feed.
If shrimp show severe stress (lying on their sides, frantic swimming), perform an immediate 50% water change to dilute the medication.

Day 3: Second Dose

Apply a second dose at the same concentration as the first.
This catches any planaria that hatched from eggs after the first dose (planaria eggs are often resistant to a single treatment).

Day 5–6: Third Dose (Optional but Recommended)

A third dose provides insurance against any remaining eggs or resistant individuals.
Particularly important in heavily infested tanks.

Day 7: Water Change and Clean-Up

Perform a 50% water change with dechlorinated water, matching temperature and TDS to your tank parameters.
Vacuum the substrate to remove dead planaria remains.
Reinstall activated carbon in the filter to remove residual medication.
Turn UV steriliser back on if applicable.

After Treatment: Clean-Up and Monitoring

Treatment does not end with the last dose. Proper follow-up is essential to prevent a recurrence and to manage the aftermath.

Removing Dead Planaria

Dead planaria decompose quickly in Singapore’s warm water (28–32 °C), which can cause an ammonia spike if there were large numbers. Siphon out as many dead worms as you can see during and after treatment. Pay special attention to crevices in hardscape and dense plant areas where dead worms may accumulate.

Monitoring Schedule

Week 1 after treatment: Check glass and substrate nightly with a torch for surviving planaria. If you spot any, consider a fourth dose.
Week 2–3: Continue nightly checks. Planaria eggs can take up to two weeks to hatch.
Week 4 onwards: If no planaria are spotted for two consecutive weeks, the treatment was successful.

Water Quality

Test ammonia and nitrite daily for the first week after treatment. The decomposition of dead planaria, combined with any disruption to beneficial bacteria from the medication, can cause temporary spikes. Have dechlorinated water ready for emergency water changes if ammonia or nitrite becomes detectable.

Trapping as a Supplementary Method

Planaria traps can be used alongside chemical treatment or as a monitoring tool. They are not effective enough as a sole treatment method for a serious infestation, but they serve useful supplementary roles.

How to Make a Planaria Trap

Take a small glass or plastic container (a shot glass or small jar works well).
Place a small piece of raw meat, shrimp, or fish inside as bait.
Cover the opening with a piece of stocking or fine mesh, secured with a rubber band, with a small hole cut in the centre (just large enough for planaria to enter).
Alternatively, use a commercial planaria trap — these are available from most Singapore aquarium shops.
Place the trap on the substrate at night and remove it in the morning.

Trapping reduces the population but cannot eliminate it. Even aggressive trapping over weeks will not catch every individual, and the remaining planaria will reproduce. Use trapping to reduce numbers before chemical treatment, or as a post-treatment monitoring tool to check for survivors.

Prevention: Stop Planaria Before They Start

Prevention is always preferable to treatment. Planaria enter tanks primarily through:

Contaminated plants — plants from tanks with planaria can carry worms or eggs. Quarantine new plants and inspect carefully.
Contaminated substrate or hardscape — used substrate and driftwood from infested tanks can harbour planaria.
Live food — blackworms, tubifex and other live foods can introduce planaria.
Overfeeding — this is the number one factor that allows planaria populations to explode. Excess food on the substrate feeds the worms and fuels rapid reproduction.

Prevention Strategies

Feed conservatively — in a shrimp tank, feed only what can be consumed within 2–3 hours. Remove uneaten food promptly.
Quarantine new additions — keep new plants in a separate container for one to two weeks and inspect for planaria before adding to the main tank.
Use tissue culture plants — these are grown in sterile conditions and guaranteed pest-free.
Maintain good hygiene — regular substrate vacuuming and water changes reduce the organic matter that planaria feed on.
Avoid cross-contamination — do not share nets, siphons or equipment between tanks without sanitising.

For more on planaria biology and identification, see our comprehensive planaria aquarium guide. For general shrimp tank maintenance practices that help prevent pest outbreaks, our cherry shrimp care guide covers the fundamentals.

Frequently Asked Questions

Will No Planaria kill my snails?

At recommended doses, No Planaria is generally tolerated by most snail species. However, sensitivity varies — Malaysian Trumpet Snails and Ramshorn Snails tend to be more resilient, while some hobbyists report Nerite Snails showing stress at treatment concentrations. If you have valuable snails, dose conservatively (start at half dose) and monitor closely. If in doubt, remove snails before treatment.

Can I use salt to kill planaria in a shrimp tank?

No. The salt concentration required to kill planaria (approximately 1–2 tablespoons per litre) is far higher than what shrimp can tolerate. Salt is not a viable planaria treatment for shrimp tanks. Stick to No Planaria or fenbendazole.

How did planaria get into my tank if I only used tissue culture plants?

Planaria can enter through routes other than plants. Contaminated equipment (shared nets, siphons), live food, used hardscape or substrate, and even water from other tanks can introduce them. Once a single planaria enters a well-fed tank, the population can grow rapidly — they reproduce both sexually and asexually (through fission).

I treated with No Planaria but they came back after a month. What went wrong?

Most likely, eggs survived the treatment and hatched after it ended. Planaria eggs are more resistant to treatment than adult worms. This is why the three-dose protocol (days 0, 3, and 5–6) is important — it catches worms hatching from eggs after the first dose. If planaria return, repeat the full protocol and ensure you complete all three doses. Also reassess your feeding habits — if the food supply remains abundant, even a few survivors can repopulate quickly.

Get Expert Help with Planaria

Dealing with a planaria outbreak can be stressful, especially when valuable shrimp are at risk. Visit us at Gensou, 5 Everton Park, Singapore, and our team can help you identify the specific worms in your tank, recommend the right treatment, and guide you through the process. With over 20 years of hands-on experience, we have seen and solved every shrimp tank pest problem imaginable. Contact us any time.

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