Terror Of The Deep, Marine Velvet, A Silent Killer

| Updated: July 13, 2023
Emporer Angelfish showing signs of marine velvet disease

If you love your saltwater aquarium fish, you need to watch out for marine velvet. This sneaky disease can wipe out your entire tank in a matter of days, leaving you heartbroken and frustrated. Marine velvet, also known as amyloodinium ocellatum, is one of the most common and deadly diseases that affects marine fish. It’s caused by a tiny parasite that sucks your fish’s blood and life out, making them suffocate and rot. Marine velvet can infect any fish species, but some are more prone to it than others, such as tangs, angelfish, butterflyfish, and wrasses.

In this article, we’ll tell you everything you need to know about marine velvet, how to spot it, how to treat it, and how to prevent it. We’ll also show you how to tell it apart from another similar disease called ich, which is often mistaken for marine velvet. By the end of this article, you’ll be able to protect your fish from this silent killer and enjoy your aquarium for years to come.

What is Marine Velvet and How Does It Kill Fish?

Marine velvet is a disease caused by a microscopic parasite called Amyloodinium ocellatum. This parasite belongs to a group of organisms called dinoflagellates, single-celled creatures with whip-like tails that help them move. Some dinoflagellates are harmless and live freely in the water, while others are nasty and cause diseases in fish and other animals.

Amyloodinium ocellatum is one of the nasty ones. It has a complicated life cycle that involves three stages: trophonttomont, and dinospore. The trophont stage is when the parasite sticks to the skin or gills of your fish and feeds on its blood and tissue. This stage lasts for about 3 to 7 days. The tomont stage is when the parasite leaves your fish and forms a hard shell on your tank’s rocks or other surfaces. This stage lasts for about 12 to 18 hours. In the dinospore stage, the shell breaks open and releases hundreds of tiny spores that swim around, looking for new fish to infect. This stage lasts for about 12 to 48 hours.

The parasite can attack any part of your fish’s body, but it loves the gills because they are full of blood and oxygen. The parasite destroys the gills, causing inflammation, bleeding, tissue death, and impaired breathing. Your fish will struggle to breathe, get less oxygen in their blood, and eventually suffocate. The parasite can also attack the skin, causing wounds, ulcers, mucus production, and scale loss. Your fish will feel irritated, stressed, lose appetite, lose weight, and get weaker.

Marine velvet is very contagious and can spread like wildfire in your tank. It can be passed on through direct contact between infected and healthy fish or through water or equipment that carries the parasite’s spores. The parasite can survive in different levels of saltiness and temperature, making it very tough and adaptable.

Spotting Marine Velvet… Before It’s Too Late

Marine velvet can be tricky to diagnose because its symptoms are often mild (until they aren’t) or similar to other diseases. The most obvious sign of marine velvet is the appearance of many small white dots on the body and fins of your fish. These dots are actually the trophonts (feeding parasites) buried in your fish’s skin or gills. The dots may look like dust or salt sprinkled on your fish’s body. However, these dots are not always easy to see, especially in dark-colored or thick-scaled fish. You might need a microscope or a magnifying glass to see them.

Another sign of marine velvet is the way your fish act. Infected fish will show signs of discomfort and distress, such as scratching or rubbing against objects (flashing), swimming erratically or near the surface or flow of wavemakers (gasping), hiding or isolating themselves from other fish (lethargy), or losing interest in food (anorexia). These signs show that your fish have trouble breathing or feel itchy because of the parasite.

A third sign of marine velvet is how your fish look. Infected fish will show signs of deterioration in their appearance and health, such as pale or dull coloration (anemia), sunken eyes (dehydration), clamped fins (stress), or open wounds or ulcers (infection). These signs show that your fish are losing blood, fluids, and tissue because of the parasite’s feeding and damage.

The best way to confirm if your fish have marine velvet is to take a sample of their skin or gills and look at it under a microscope. You’ll be able to see the parasite as oval-shaped cells with a brownish pigment and two tails. However, this method may not be possible for most hobbyists, as it requires special equipment and skills. Another option is to use a test kit that detects the parasite’s DNA in the water. This method is more convenient and accurate but may be expensive and hard to find.

How to Treat Marine Velvet and Save Your Fish?

Marine velvet is a very aggressive and fast-acting disease that can kill your fish in a matter of days if you don’t treat it right away. Therefore, you need to act quickly and decisively as soon as you notice any signs of infection. Here are some steps you can take to treat marine velvet and save your fish:

  • Quarantine the infected fish. The first step is to separate the infected fish from the rest of the tank in a different tank. This will stop the disease from spreading and allow you to treat the fish more effectively. The quarantine tank should have good water quality, filtration, aeration, heating, and lighting. It should also have some hiding places and decorations to make the fish feel more comfortable and less stressed. The quarantine tank should be kept empty (without any fish) for at least 6 weeks after the last sign of infection. This will make sure that all the parasite’s stages are gone from the tank.
  • Use proper medication. The second step is to use effective medications that can kill the parasite in all its stages. Many medications are available for treating marine velvet, but not all are safe or suitable for all fish species or reef tanks. Some of the most popular medications are:
    • Chloroquine phosphate: This is a medicine that is used to treat malaria in humans, but it also works very well against marine velvet. It works by messing up the parasite’s metabolism and reproduction. It can be used as a bath or an oral treatment. The recommended dose is 10 mg per liter of water for a bath or 40 mg per kg of body weight for an oral treatment. The treatment should last for 10 days. Chloroquine phosphate is generally safe for most fish species but may harm some invertebrates and corals in reef tanks. It may also make the water blue-green.
    • Copper: This is a metal that has been used for a long time to treat various parasitic diseases in fish. It works by breaking down the parasite’s cells and membranes. It can be used as a bath or an oral treatment. The recommended dose is 0.15 to 0.2 mg per liter of water for a bath or 5 mg per kg of body weight for an oral treatment. The treatment should last for 14 days. Copper is effective against marine velvet, but it can be toxic to some fish species, especially those without scales, as well as invertebrates and corals in reef tanks. It may also affect the biological filtration and water quality in the tank.
    • Methylene blue: This is a dye that has antiseptic and antiparasitic properties. It works by making the parasite’s cells oxidize and stop breathing. It can be used as a bath or a dip. The recommended dose is 3 mg per liter of water for a bath, or 15 mg per liter of water for a dip. The bath treatment should last for 10 days, while the dip treatment should last for 30 minutes. Methylene blue is safe for most fish species but may harm some invertebrates and corals in reef tanks. It may also make the water blue.
  • Support your fish’s health. The third step is to give your fish the best care and conditions possible to help them recover from the infection and boost their immunity. Some of the things you can do are:
    • Keep the water quality high: Water quality is vital for the health and well-being of your fish. Poor water quality can stress your fish and lower their resistance to diseases. You should test your water parameters regularly and do frequent water changes to keep them within the ideal ranges. You should also use activated carbon or other chemical filtration media to remove any medication residues or toxins from the water.
    • Feed them well: Food is another important factor for your fish’s health. Good food can give your fish the essential nutrients, vitamins, minerals, and antioxidants that can improve their immune system and healing process. You should feed your fish a varied diet that includes high-quality pellets, flakes, frozen, live, or freeze-dried foods that are suitable for their species and needs.
    • Reduce stress: Stress is another factor that can weaken your fish’s immune system and make them more prone to diseases. You should try to minimize any sources of stress for your fish, such as overcrowding, aggression, noise, or sudden changes in temperature, lighting, or water parameters. You should also provide your fish with enough hiding places, plants, rocks, or other decorations that can make them feel more comfortable and secure in their tank.
    • Watch them closely: The last step is to keep an eye on your fish’s condition and behavior during and after the treatment. You should check on your fish daily and look for any signs of improvement or worsening. You should also regularly test and adjust the water parameters and medication levels as needed. If you notice any negative reactions or side effects from the medication, such as loss of color, appetite, or activity, stop treatment immediately and consult a vet or an expert.

How to Prevent Marine Velvet from Ruining Your Tank?

The best way to prevent marine velvet is to stop it from entering your tank in the first place. This can be done by following some simple precautions and preventive measures, such as:

  • Quarantine new fish: One of the most common ways of bringing marine velvet into your tank is by adding new fish that are already infected or carrying the parasite’s spores. To avoid this, you should always quarantine any new fish that you buy or receive for at least 4 weeks in a separate tank before adding them to your main tank. This will let you observe the fish for any signs of disease and treat them if needed. You should also avoid buying fish from unreliable sources or fish that look sick or stressed.
  • Disinfect equipment and water: Another way to bring marine velvet into your tank is by using contaminated equipment or water containing the parasite’s spores. To avoid this, you should always disinfect any equipment or water that you use for your tanks, such as nets, buckets, hoses, siphons, filters, heaters, or decorations. You can use bleach, vinegar, boiling water, or other disinfectants to kill any parasites or pathogens that may be present. You should also rinse and dry the equipment or water thoroughly before using it.
  • Maintain good hygiene and sanitation: A third way of bringing marine velvet into your tank is by transferring it from your hands, clothes, or other objects that may have touched infected fish or water. To avoid this, you should always wash your hands and change your clothes before and after handling your fish or working on your tank. You should also avoid touching or moving any objects that may have been exposed to infected fish or water without disinfecting them first.
  • Boost your fish’s immunity: A fourth way of preventing marine velvet is by strengthening your fish’s immune system and making them more resistant to diseases. This can be done by providing them with optimal care and conditions, such as good water quality, nutritious food, a stress-free environment, and adequate space and companionship. You can also add some immune-boosting supplements to their diet, such as garlic, vitamin C, probiotics, or herbal extracts.

The Differences Between Marine Velvet and Ich

Marine velvet and ich are 2 of the most common and deadly diseases affecting saltwater aquarium fish. They are both caused by parasitic dinoflagellates that infect the skin and gills of the fish and cause similar symptoms. However, they are not the same disease and have some key differences that you should know:

  • The cause: Marine velvet is caused by Amyloodinium ocellatum, while Cryptocaryon irritans cause ich. They are both dinoflagellates but belong to different groups and have different shapes and life cycles.
  • The size: Marine velvet is smaller than ich. Marine velvet’s trophonts (feeding parasites) are about 30 to 60 micrometers in diameter, while those of ich are about 200 to 1000 micrometers in diameter. This means that marine velvet is harder to see with the naked eye than ich.
  • The speed: Marine velvet is faster than ich. The life cycle of marine velvet takes about 4 to 7 days, while that of ich takes about 10 to 28 days. This means that marine velvet can kill your fish quicker than ich.
  • The treatment: Marine velvet is harder to treat than ich. Some of the medications that work for ich may not work for marine velvet, such as copper. Some medications that work for marine velvet may be unsafe for some fish species or reef tanks, such as chloroquine phosphate. Therefore, you need to be more careful and selective when choosing a medication for marine velvet.

Marine Velvet vs. Freshwater Velvet

Don’t confuse marine velvet with freshwater velvet, a similar disease that affects freshwater fish. They are both caused by tiny parasites but differ in many ways. Freshwater velvet looks like gold dust on your fish’s body and fins, while marine velvet looks like white dots. Freshwater velvet needs acriflavine, formalin, or malachite green to treat it, while marine velvet needs chloroquine phosphate, copper, or methylene blue. These diseases have different hosts, symptoms, treatments, and prevention methods. Last but certainly not least, the biggest difference is in the names; marine velvet lives in saltwater, and freshwater velvet lives guessed it, freshwater.

Final Words

Marine velvet is a deadly disease that can affect any saltwater aquarium fish. It’s caused by a tiny parasite that feeds on the blood and tissue of the fish and causes severe respiratory and skin problems. It can be hard to spot and treat and can spread quickly in your tank. Therefore, you need to know how to identify, treat, and prevent this disease.

In this article, we’ve told you everything you need to know about marine velvet, how to recognize its symptoms, how to treat it with proper medication and supportive care, and how to prevent it from entering your tank. We’ve also shown you how to tell it apart from another similar disease called ich, which is often confused with marine velvet. We hope that this article has been helpful and informative for you and your fish.

Thank you for reading this article. If you have any questions or comments, please feel free to contact us or leave a comment below. We’d love to hear from you and help you with your aquarium needs.

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Shayna Easton
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