How to Remove Worms From a Fish Tank

Medically Reviewed by Vanesa Farmer, DVM on July 13, 2023
4 min read

When you establish an aquarium, you want to ensure a safe and healthy environment for your new pets. Over time, you may introduce new fish and plants. This leaves you at risk for introducing new bacteria, parasites, and even worms to your tank. 

You can take measures to avoid developing a worm problem. If you do find yourself deworming a fish tank, follow these steps and tips to make the process easier.

Detritus worms are annelid worms and are very similar to earthworms and leeches. They are so tiny that, at first, you may not even notice them in your tank. Detritus worms are thin, pointy, and a white-brown color. 

You’ll see them in the sand or pebbles of your tank. This particular type of worm eats decomposing fish and plant waste and will not harm your fish. In fact, they are very common in aquariums. Overall, they are beneficial in helping clean your tank and maintaining a healthy balance in your tank’s ecosystem. 

Detritus worms may become a nuisance if they are overpopulated in your aquarium. This happens when you don’t clean your tank regularly. As detritus worms multiply, their food and oxygen sources are reduced. This causes them to climb up the tank toward the water’s surface.

Traditional dewormers do not work on detritus worms and may actually cause harm to your pets, so avoid using them in your tank. Instead, focus on giving your tank a proper cleaning. While you won’t completely rid your tank of detritus worms, you can get their population back down to a manageable level.

Worm removal begins by giving your tank a thorough cleaning. 

Unplug your equipment. If your filter is left on, it could be damaged during cleaning.

Gather your supplies:

  • Two clean buckets
  • Sponges
  • Gravel or sand siphon
  • Replacement water

Prepare your buckets. Use one bucket to siphon out the worms and other debris and a second one to pour in fresh water.

Remove worms. Work methodically using a sand or gravel siphon this is called vacuuming to remove the worms from the sides and bottom of your fish tank. Make sure you don’t remove more than 10%-15% of the water in the process.

Refill your tank. Slowly add in the amount of water you removed while cleaning. Test the water to ensure you reach the appropriate pH and saline levels. Plug your filter in to remove any remaining debris floating around.

If needed, repeat this process each week for several weeks until you reach your desired results. Then be sure to maintain the cleanliness of your tank consistently, so you don’t have too many worms again.

Planaria worms are less common than detritus worms and are much harder to remove. Planaria are flatworms and most often enter aquariums via live pond plants. They most frequently occur in natural water sources and easily transplant into aquariums. Both freshwater and saltwater aquariums are at risk for developing planaria worms. 

While small, if you pay close attention, you will see them crawling across the glass inside an aquarium. Because they do not require mating to reproduce, they are difficult to remove completely. In fact, if you cut one in half, it simply results in two worms. 

While they are scavengers, similar to detritus worms, they are dangerous because they are also carnivores. They may not harm your healthy adult fish, but can prey on fish eggs, babies, and weak adults.

Getting rid of planaria worms requires chemical treatment. Since chemicals are dangerous for your fish, have a professional confirm their presence before attempting treatment. 

Research all of your options before choosing a chemical treatment. If possible, consult with a vet about which ones are safe for your particular breed of fish. Invertebrate species like snails and shrimp are particularly at-risk and should be removed. Sharks, silverfish, lionfish, piranhas, bottom feeders, and certain scaleless or Metynnis fishes may also be more likely to have a reaction to deworming chemicals. 

With all chemicals, be sure to use the exact dosage recommended by the manufacturer. Too much of the chemical will also harm or kill your fish.

Quarantine new fish. Talk to your vet or pet store before introducing new fish to a tank. When you purchase a new fish from a breeder or pet store, you can’t be sure it is completely healthy. 

That’s why it’s a good idea to keep new fish separated before adding them to your existing aquarium. This allows time for you to assess your new pet’s health and behaviors looking for signs of worms, parasites, or other health issues.

Find a fish veterinarian. You don’t want to find yourself scrambling to find a professional in your moment of need. It’s a great idea to establish a relationship with a veterinarian in your area to call for questions and checkups. 

Since not all veterinarians treat fish, you’ll want to do some research and find a specialist in your area.

Signs of fish illnesses. Even if you don’t see worms in your fish tank, you can watch for signs that your fish is sick. If you have any concerns about your fish’s health, check with your veterinarian. There are a number of signs you should watch for that may indicate your fish is sick:

  • Being disoriented
  • Swimming in an odd pattern or upside down
  • Not eating
  • White spots appearing on scales or gills
  • Discoloration
  • Trouble breathing, such as staying at the surface of water
  • Bulging eyes
  • Mucus appearing on the body
  • Rubbing against hard surfaces
  • Isolating oneself from other fish
  • Sores
  • Bloating
  • Change in shape, size, or appearance