Velvet Disease in Fish: Symptoms, Causes, and Treatment

Updated on August 14, 2019
mercurio profile image

I write articles about fish care, focusing especially on diseases and stress.


Velvet disease is a condition characterized by a yellowish, dusty aspect on the skin of the fish. The disease manifests itself as a fine dust that is typically gray-yellow in color, which explains why this disease is also also known as rust disease or gold-dust disease.

  • The causative agent is a protozoan with a biological cycle similar to the causative agent of the white spot disease.
  • The agent of velvet disease is the dinoflagellate Oodinium pillularis discovered by Schaperclaus in 1951. Oodinium is round or oval in shape (pear-shaped).
  • Different species of the genus Oodinium include: pillularis, cyprinodontum, limmeticum, and ocellatum.
  • It attacks most types of ornamental fish (although Oodinium ocellatum is particular to marine fish) and is a major cause of mortality of the offspring.


The symptoms depend mainly on the severity of the infection.

  1. During the beginning of the infection, the affected fish will show some behavioral changes, like fin twitching or body rubbing.
  2. As the disease advances, the skin of the sick fish becomes dusty and opaque due to the excess of mucus that their immune system generates as a defense mechanism.

Since the parasite affects the gills, it is common that respiratory failure appears.

If the condition becomes severe, the fish may present the following:

  • Opaque eyes
  • Fins against the body
  • Ulcers in the skin
  • Skin detachment
  • Exophthalmia

Pathological Physiology

Oodinium has a life cycle very similar to the Ichthyophthirius (white spot disease); however, these organisms are not related—Oodinium is a flagellate, whereas Ichthyophthirius is a ciliate.

  • During the infecting phase, the parasite feeds on live organic matter through roots that it uses to attach to the skin.
  • In the free phase, a protective shell forms on the inside, which then reproduces by cellular division. It can produce more than three hundred spores.


Velvet disease is a common occurrence in aquariums that undergo poor maintenance conditions. The following factors influence this:

  • Abrupt changes in water temperature
  • Introduction of new fish without quarantine
  • Tired fired that are lacking in defenses
  • Old water—you should be frequently changing your water.
  • Introduction of plants with cysts (if bringing in new plants, make sure to disinfect them prior to their introduction)

Biological Cycle of the Parasite

The protozoa begins the parasitosis in the gills, then it complete the infecting phase when it begins feeding from the host fish, until it reaches maturity.

During the biological cycle, the parasite presents the following phases:

  • Infecting phase, which is immobile in the skin (during this stage, it feeds and grows).
  • Cyst phase in the substrate, when the parasite exits the fish. Multiplication by cellular division takes place inside the cyst in this phase.
  • Dinospores phase. The dinospores are the product of the divisions of the previous phase. If dinospores don't find a new host, they die within 24 to 36 hours.

The life cycle is completed in ten to fourteen days at a temperature of 23 to 25 degrees.


Treatments commonly involve copper salts. Since not all fish tolerate this type of medication, take caution before applying. Here are some other alternatives:

  • Quinine salts or methylene blue.
  • Some species of the parasite also obtain energy through photosynthesis. Try to cover the aquarium, which can help weaken the parasite.
  • Increasing the temperature of the water can also help with treatment because the parasite's life cycle is accelerated through the heat.


Successful prevention requires first knowing how the disease entered the aquarium.

  • The parasite can be latent, waiting for a favorable condition. When the fish are weakened—often due to stress—the disease then attacks.
  • Stress can be due to poor maintenance conditions of the water or abrupt changes of temperature when making the water replacements.
  • Parasite cysts can also enter through sick new fish or through infected objects. To further prevent this, make sure you quarantine any new fish or objects and ensure hygiene before introducing them to the tank.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.


Submit a Comment

No comments yet.


This website uses cookies

As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

Show Details
HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
LoginThis is necessary to sign in to the HubPages Service.
Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
AkismetThis is used to detect comment spam. (Privacy Policy)
HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
MavenThis supports the Maven widget and search functionality. (Privacy Policy)
Google AdSenseThis is an ad network. (Privacy Policy)
Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
Index ExchangeThis is an ad network. (Privacy Policy)
SovrnThis is an ad network. (Privacy Policy)
Facebook AdsThis is an ad network. (Privacy Policy)
Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
AppNexusThis is an ad network. (Privacy Policy)
OpenxThis is an ad network. (Privacy Policy)
Rubicon ProjectThis is an ad network. (Privacy Policy)
TripleLiftThis is an ad network. (Privacy Policy)
Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
ClickscoThis is a data management platform studying reader behavior (Privacy Policy)