Marine Velvet – Surviving and Preventing A Tank Terror

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Have you come to this post wondering if your fish has Marine Velvet? I feel your pain if you have. In my over 25 years of experience, Marine Velvet is the most common disease tank crasher in the hobby. It strikes fast, kills fast, and most people aren’t prepared for it. It’s the one disease I fear the most in my saltwater aquarium. In fact, it is labeled one of the deadly three in my how to quarantine saltwater fish post.

In this post, I will go through everything you need to know to fight this deadly disease. You will learn what it is, its life cycle, how to treat it, and how to prevent it. It is a true tank terror and I’m not going to sugarcoat it. If your tank has it right now, chances are one or more of your fish will succumb to this disease. Let’s get started on what you need to know first.

What You Need To Know (The Facts)

NameAmyloodinium ocellatum
Common TreatmentsChloroquine Phosphate or Copper
Short-Term TreatmentAcriflavine or Formalin bath
CausesTransferred from infected fish, corals, or water
Fallow Period6 weeks
Common SymptomsNumerous white dots on the body, fins, flashing, swimming to flow of wavemakers

What is Marine Velvet? (Amyloodinium ocellatum)

Marine Velvet, scientifically known as Amyloodinium ocellatum is a dinoflagellate (not the same brown stuff mentioned in my other post). It is well known for killing prized saltwater fish in less than 24 hours, and it spreads the most during the warmest months of the year in the aquarium trade. If you are well versed in the hobby, you will often hear of increased cases of this disease during the summer. It makes summer one of the riskiest times to purchase fish locally or online.

Because it is a dinoflagellate, it has unique features compared to other diseases in our hobby. It is often mistaken as ich (Cryptocaryon irritans), and because of this you should learn the differences between the two.

Marine Velvet vs Ich – The 4 Key Differences

It’s very easy to confuse these two diseases. I’ve heard many folks say, “ich wiped my tank.” However, their stories, of how quickly everything happened, made me suspect it was actually Velvet. Let’s go into the four main differences so you know what you are tackling. They are:

  1. The number of spots
  2. Type of free swimmers
  3. Life cycle
  4. Time of infection

1. The Number of Spots

Your first indicator is usually the number of spots. Ich’s white spots are spread out and easy to count. With Velvet, the spots are so numerous it’s difficult to count them all. It’s almost as if the fish was dusted with white power (source). You can see an example of both diseases below. Note how the purple tang has spots spread out while the Achilles tang has spots all over its body, including the eyes.

2. Type Of Free Swimmers

Because Marine Velvet disease is a dinoflagellate, the free swimmers are called dinospores, while ich’s are called theronts. While this is a technical term, one thing to know is that dinoflagellates feed off sunlight which makes it susceptible to blackouts, UV, and Ozone – though once you have an outbreak you will need to take more extreme measures to fight it off. All of these will control the spread, but will not cure an already infected fish!

3. Life Cycle

Velvet averages a 4-day life cycle and there are more attacking free swimmers than ich. This is why they can overwhelm and kill fish so fast. Ich’s life cycle can be as long as 2 weeks.

4. Time Of Infection

Because Velvet is a dino, it remains infective for up to 15 days. This is because as dinos, they can feed off sunlight. Ich is only infectious up to 48 hours. The fact that it remains infective longer and attacks in larger numbers and longer is what makes this disease far deadlier than ich.

Marine Velvet Life Cycle

As I mentioned before, the life cycle is only 4 days and starts when a Velvet dinospore attaches to a fish’s skin. The attached dinospore is then called a trophont. This trophont will feed on your fish for several days before detaching. Sometimes, the trophonts are so numerous and overwhelming that it will kill the fish before it shows any symptoms.

Once the trophont detaches, it is called a tomont. These tomonts divide until they burst. When they burst, they become new dinospores. These dinospores then attach to a new host, starting the lifecycle all over again.

Let’s illustrate this lifecycle with an image. The image below is from Dr. Fish himself, Humblefish. He is the go to for all marine fish diseases in our hobby. Check out his site for further info on all other saltwater aliments and treatments.

Marine Velvet Life Cycle

Marine Velvet Treatment (How To Cure)

Marine Velvet needs to be treated ASAP. You need to treat it in a quarantine tank as all effective medications against it are not suitable to be used in a reef or display tank. There are several steps you will need to take:

  • Get the proper medication
  • Get a test kit
  • Set up a quarantine tank
  • Perform short-term relief procedures
  • Perform treatment procedures

1. Get The Proper Medication

Step number 1 here. The preferred treatment option for Velvet is chloroquine phosphate. Unfortunately, due to the COVID-19 pandemic and its mass usage for treating malaria1 , it is getting difficult to find. Even with a vet, most are now reluctant to prescribe it to a hobbyist. Choloroquine phosphate is highly effective and can be used with no ramp up time. However, given its lack of availability, it will not be your primary treatment option.

Copper is your new go-to treatment option. We will need to do some additional steps to make it work against Velvet. There are two types of copper: ionic and chelated. Ionic copper is what you will find in most fish stores due to the availability of SeaChem Cupramine. It has a shorter range of therapeutic levels (0.4 – 0.5 mg/L) and degrades fast. It’s not my preferred choice.

Chelated copper is stable and has a larger range of therapeutic levels. Fish are more tolerant to it than ionic copper, and it is generally more effective against diseases than ionic copper. My preferred choice for chelated copper is Copper Power by Endich. Make sure you get the blue version, as there is a green version that is exclusive to freshwater Velvet. The effective range for chelated copper is 1.5 to 2.0 PPM. If you want research backed info of copper medications – see this write up from the University of Florida (UF is also the source of my featured image).

My Pick
Copper Power

The Most Available Velvet Mediciation

Copper Power is Chelated Copper that is more stable than Cupermine and easier to use

Buy On Amazon Click For Best Price

Unfortunately, most stores will not have Copper Power in stock. Amazon Prime is your best bet for fast delivery. If you are researching this article and do not have a fish that is sick, I would purchase some now. It has a long shelf life.

2. Get A Test Kit

If you manage to get your hands on chloroquine phosphate, you are in luck. You do not have to use a test kit for CP because there is none available to the hobbyist. Only lab grade equipment can test for CP and that is way out of the price range of most people, and also not available to purchase unless you are a lab tech.

If you get copper, you will need a test kit. There are many factors with copper that call for a test kit. For one, copper gets absorbed by lots of things in your aquarium – your filter, the silicone in your aquarium, and any decorations. This is why hospital tanks are set up with PVC piping and simple power filters or sponge filters.

Of all copper test kits available, the best out there is the Hanna Checker

My Pick
Hanna Instruments Copper Test Kit

Best Copper Test Kit Available

Extremely precise and reliable, this is the only copper test kit you should use when treating marine fish diseases

Buy On Amazon Click For Best Price

3. Set Up A Quarantine Tank

A proper quarantine (AKA hospital tank) is a must. You will need to remove all fish from your display tank as the disease will need to be starved out of your display. More on this later when I explain the fallow period. Depending on the number and size of fish, most people will be working with a 10, 20L, or 55 gallon tank when treating for Velvet. I prefer the 20L gallon since it is a nice combo of size, space, and cost-effectiveness. A 55 gallon tank is used for large or multiple fish. Ammonia levels should be monitored with a SeaChem Ammonia Alert Badge.

For the full setup you will need:

  • An aquarium
  • Small power or airpump
  • Power Filter or Sponge Filter
  • Heater
  • Thermometer
  • 2-3″ PVC Elbow
  • Cover – to prevent fish from jumping

I walk you through the part selection below in my video. I bookmarked it to the section where I go through each piece of equipment.

The main concern with a hospital tank is not having a bacteria culture to jumpstart it. If you have media in your display tank, move it over to the hospital tank to seed the tank. I would also recommend using Bio-Spera. This is my preferred choice for bacteria in a bottle for hospital tanks because you can find it everywhere – even in chain pet stores.

4. Perform Short-Term Relief Procedures

Because most of you will need to use copper to treat Marine Velvet disease, you will need to perform short-term relief procedures to give your fish relief from the disease. To do so, we will want to use an Acriflavine or Formalin bath. Since Formalin is a controversial medication and even banned in some states, Acriflavine is going to be our best choice.

There is actually one product in our hobby that contains both Acrifalvine and Formalin, That product would be Ruby Reef Rally. This is the preferred solution for providing relief to our fish. Here are the steps:

  • Prepare a 2.5 gallon or 5 gallon bucket depending on your fish size with a heater and air pump
  • Put your display tank water into the bucket
  • Add the recommended dosage of Ruby Reef Rally to the bucket and mix fully
  • Place fish into the bucket and allow 90 minutes observing for signs of stress
  • Remove fish and place into your hospital tank – start next relief procedures

Rally is my go to for dips. I use it for disease relief and also before I introduce any fish into my quarantine tanks. It is available at most local fish stores.

If you are unable to procure Rally, you can do a 5-minute freshwater dip. Walking through on a freshwater dip can be a separate article in itself. Here is a video from Meredith Presley to get you going. She does this for gill flukes, but a freshwater dip is an effective short-term option for Marine Velvet disease.

5. Perform Treatment Procedures

It’s time to attack this disease full-on. Since there are two ways to tackle this beast, I’ll walk you through both.

Treating With Chloroquine Phosphate

If you are fortunate to get this wonder drug, here is how you eradicate Velvet with it:

  • Typical dosage is 40mg per gallon
  • Use a digital scale when measuring your dosage
  • Use your hospital tank water in a cup to pre-dissolve the solution
  • For Velvet – you will need to maintain 40 mg per gallon for at minimum 14 days to treat – 30 days is preferred
  • If a water change is done, you must replace the water with medicated water using the same 40mg per gallon dosage
  • For top off water, you will not need to add medication

I provided my video again, this time at the 7:00 mark where I walk you through how I mix CP in my quarantine tanks. You can see how I use the digital scale to measure, how I pre-dissolve, and how I add it to the aquarium.

Treating With Copper

Copper is a bit tricky because we have to work with the ramp up time. Most fish cannot tolerate an instant ramp up to therapeutic ranges. This is why we need to perform those short term procedures I explained previously to buy us time. We will need to perform a 24-hour ramp up. Here are the steps to getting us to effective levels:

  • Start off by raising copper levels to 1.0 ppm – verify with your Hanna Checker
  • Over the next 24 hours – raise your levels to 1.5 ppm. Do this every 8 hours, raising 0.125 PPM each time
  • After you raise to 1.5 ppm – bring to 2.0 ppm over the next 24 hours. Do this every 8 hours, raising 0.125 PPM each time
  • Treat for 30 days keeping levels above 1.50 ppm. If you drop below 1.50 at any time, your countdown to 30 days starts over!

The Marine Velvet Fallow Period – How to Eradicate The Disease In Your Display Tank

Treating the disease in the hospital tank and saving your fish is the first battle we fight. Completely eradicating Velvet from your display is how to get total victory. To do this, we must understand the fallow period needed to wipe it out. I also need to explain what fallow means.

Fallow means no fish in your display. Velvet needs the fish as a host, without the fish, the disease starves out and can’t reproduce. Any corals, inverts, and clean up crew you have in your display can stay in your tank. This can be really discouraging for a reefer to have a fishless tank. There have been times that I have recommended to a hobbyist to impulse buy corals when in the beginning of the fallow period. Just buy a bunch now.

Why would I say that? Because after you place all those corals you always wanted, you can begin your fallow period. It’s something you can look forward to. When your fish return they will be treated to new corals and structures to explore in a disease free tank! The fallow period is also a long time.

How long is it? The fallow period needed to completely wipe out Velvet from a display tank is 76 days. Yes, I know that is a long time. Now you see why I’m suggesting you go buy those corals you always wanted now where there is no risk to spread disease to your fish!

During this time, you must make sure you do not cross contaminate your tanks. Keep your hospital tank 10 feet away from your display tank and use separate nets, buckets, and equipment. Make sure you wash your hands before switching tanks with a reef safe cleaner like dawn dish soap.

Frequently Asked Questions

I’m going to add some FAQS here that I get from readers and also to help with visibility online so people can find this post. If you have any questions, I encourage you to leave a comment below. I will add to this FAQ over time.

Can Fish Survive Marine Velvet?

Yes, fish can survive Marine Velvet disease. They will need treatment to survive, however. Surviving fish have been known to develop an immunity to the disease, but can still be carriers. This is why we must treat the disease and completely eradicate it from your display tank.

How Do You Get Rid Of Marine Velvet?

There are two medications that are effective in getting rid of Marine Velvet disease. The most available is chelated copper using a product like Copper Power. The other medication is chloroquine phosphate, which is more effective but difficult to obtain. Both need to be treated in a hospital tank, and a fallow period must be done in the display tank to remove it completely.

How Do You Treat Velvet?

You need to treat Velvet with either chelated copper or chloroquine phosphate in a hospital tank, then have a 76 day fallow period in your display tank to completely remove it from the system.

How Long Can Marine Velvet Live Without A Host?

Marine Velvet can live without a host fish up to 72 days per a Texas A&M study. This is why I recommend a 76-day fallow period. This builds a buffer so you can ensure complete eradication

How Long Can A Fish Live With Velvet?

It depends on the fish, but generally most fish cannot live with Velvet longer than 1-2 days. Some will die before they have any visible symptoms! This is why it’s critical for you to begin treatment as soon as possible. It is not a disease to take lightly!

The most resistant fish in our hobby are those with a thick slime coat. These would be fish like clownfish, mandarins, wrasses, and rabbitfish. Nevertheless, Velvet is capable of wiping out every fish in your aquarium!


I hope this guide got you all the information you need to combat this tank killer. Marine Velvet disease shoudn’t be taken lightly. You should run to your local fish store to get supplies now if you are dealing with it. If you are not dealing with it, work on building up your medicine cabinet now. It may save your fish’s life one day or save a fellow reefer’s fish. If you have any questions, please leave a comment below. I’ve successfully fought off Velvet in the past and I am happy to share my experience with you.

by Mark

Mark is the founder of Aquarium Store Depot. He started in the aquarium hobby at the age of 11 and along the way worked at local fish stores. He has kept freshwater tanks, ponds, and reef tanks for over 25 years. His site was created to share his knowledge and unique teaching style on a larger scale. He has worked on making aquarium and pond keeping approachable. Mark has been featured in two books about aquarium keeping - both best sellers on Amazon. Each year, he continues to help his readers and clients with knowledge, professional builds, and troubleshooting.

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