Planaria in Aquarium & Hydra in Shrimp Tanks: Identify and Remove (Malaysia Guide)

Found tiny white worms on the glass? Before you panic, check the head. Planaria in aquarium tanks have a flat body and a triangle-shaped, arrow-like head, often with two dark eye spots, and they glide smoothly. Detritus worms are thin, round, thread-like and wriggle; they are harmless. Hydra look like tiny green or white stalks with tentacles, stuck to glass or plants. Planaria and hydra both hurt shrimp tanks, especially baby shrimp, and both come from the same root cause: too much food. Cut feeding, trap the worms, and use a shrimp-safe treatment only if numbers stay high.

Identify First: Which "Cacing Putih Akuarium" Is It?

Malaysians often search cacing putih akuarium for any small white worm. There are three common culprits:

Feature	Planaria	Detritus worm	Hydra
Shape	Flat, like a tiny leech	Thin and round, like a thread	Stalk with 4–6 tentacles
Head	Triangle/arrow head, two eye spots	No visible head	Tentacles at top
Movement	Glides smoothly	Wriggles, whips about	Mostly stays fixed, stretches
Size	3–15 mm	5–20 mm	2–15 mm stretched
Colour	White, brown, grey	White, pinkish	White, green, brown
Harmful?	Yes, to shrimp and eggs	No (sign of overfeeding)	Yes, to shrimp babies and fry

A quick test: drop a small piece of meaty food in at night and look with a torch. Planaria swarm towards it; detritus worms mostly stay in the substrate.

Why Planaria in Aquarium Tanks Are a Problem

Planaria are predators and scavengers. In a fish-only tank they're mostly a nuisance. In a shrimp tank they:

• eat baby shrimp and shrimp eggs
• attack molting or weak adult shrimp
• compete for food, and multiply fast when food is abundant

They are hard to kill by cutting, since each piece can regrow into a new worm. Don't squash them in the tank.

Why Hydra Are a Problem

Hydra are tiny relatives of jellyfish and use stinging tentacles to catch prey. They feed on baby brine shrimp, copepods and, in shrimp tanks, newborn shrimp and fish fry. Adult shrimp and fish are usually safe. Hydra boom when you feed lots of baby artemia or powdered food.

Root Cause: Overfeeding

Both pests appear when there's more food than your livestock can eat. They usually arrive on plants, moss or in water from another tank, and then the leftovers let them multiply.

Before any treatment:

1. Cut feeding by half for two weeks.
2. Siphon the substrate and remove leftovers.
3. Feed only what's eaten within 2–3 hours (shrimp) or 2 minutes (fish). Good-quality shrimp food that sinks and gets eaten quickly helps.

Our guide to how often to feed fish helps you find the right amount.

Step 1: Trap Them

Planaria traps are small plastic tubes or boxes with entry holes too small for adult shrimp. Bait them with a small piece of meat, fish or shrimp pellet overnight and lift them out in the morning. You can make one from a small bottle with tiny holes drilled in the lid.

Trapping works well to bring numbers down, but rarely removes every worm.

Step 2: Shrimp-Safe Planaria Treatment

Several planaria treatment options are made for shrimp keepers. Look under pest removers and read every label.

Treatment	How it works	Shrimp safe?	Snail safe?
Betel nut (areca) based products	Natural extract that kills planaria	Generally yes at label dose	Usually yes
Fenbendazole-based products	Anti-worm drug	Generally yes for shrimp	No, kills snails
Hydrogen peroxide spot dosing	Oxidiser on worms	Risky; easy to overdose	Risky
Copper-based pest removers	Kills invertebrates	No	No

Tips:

• Dose exactly to the label and the real water volume (not the tank's nominal size).
• Remove carbon from the filter during treatment, then add it back afterwards.
• Dead planaria rot quickly, so siphon what you can and change 20–30% of water after a few days.
• Fenbendazole will wipe out snails, including nerites and ramshorns you wanted to keep. Move them out first.
• Some keepers report that treatments also kill hydra. Fenbendazole in particular is widely used for both.

Removing Hydra

1. Cut food first. Hydra starve without baby brine shrimp and fine powder food.
2. Shrimp-safe treatment: fenbendazole-based products are commonly used against hydra too (again, not snail-safe).
3. Manual removal: on glass, scrape and siphon. They regrow from bits, so remove the debris.
4. Gouramis and some fish eat hydra, but they also eat shrimp babies, so that's not ideal in a shrimp tank.

Prevention

• Quarantine new moss and epiphyte plants in a bucket for a week and inspect them
• Buy tissue-culture plants when possible
• Never pour water from another tank or from a shop bag into your tank
• Keep feeding light and siphon regularly

For the full shrimp tank picture, read the shrimp tank setup guide and kenapa udang hiasan mati. When your tank is clean again, you can restock with live shrimp from Malaysian sellers.

Frequently Asked Questions

Cacing putih kecil dalam akuarium bahaya ke?

Bergantung pada jenis. Jika cacing itu nipis dan menggeliat, ia mungkin cacing detritus yang tidak berbahaya. Jika badannya leper dengan kepala bentuk segi tiga dan bergerak meluncur, itu planaria, dan ia boleh memakan anak udang.

Macam mana nak hilangkan planaria tanpa bunuh udang?

Kurangkan makanan, gunakan perangkap planaria dengan umpan setiap malam, dan jika perlu gunakan ubat planaria yang dilabel selamat untuk udang. Elakkan produk yang mengandungi tembaga (copper).

Are detritus worms harmful?

No. They eat waste and are a sign of excess food or a dirty substrate. Feed less and siphon more and they'll drop in number.

Will fenbendazole kill my snails?

Yes. It's toxic to snails, so move any snails you want to keep before treating.

Do hydra hurt adult fish?

Generally no. Hydra mainly catch tiny prey such as baby shrimp, fry and baby brine shrimp.