Marine Velvet Disease
Amyloodinium ocellatum, commonly referred to as “velvet,” is a single celled dinoflagellate. It is sometimes referred to as a hybrid, having characteristics of both plants and animals. However, for marine aquarists it is a feared pathogen with a reputation for being capable of wiping out an entire fish population in just a matter of days.
Velvet has a lifecycle (more info here:
http://www.ultimatereef.com/articles/marinevelvet/) similar to that of Cryptocaryon irritans (ich). Even the terminology used is mostly the same - except velvet “free swimmers” are referred to as dinospores instead of theronts. Velvet’s lifecycle is typically faster (completed in 4 days on average), and the attacking free swimmers are more numerous than ich. Also, velvet dinospores can remain infective for up to 15 days, whereas with ich theronts it’s only 48 hours. This is because velvet tomonts and dinospores are both capable of using photosynthesis as a means of obtaining nutrients (remember it is a dinoflagellate).
Symptoms - Velvet dinospores will usually invade the gills first and sometimes kill the fish right then due to asphyxiation. If this happens, you may never see physical evidence of velvet on the skin & fins. Therefore, it is important to observe for these
key behavioral symptoms of velvet:
- Reduced or complete loss of appetite.
- Heavy breathing, rubbing, flashing, head twitching, erratic swimming behavior (unfortunately velvet shares all these same symptoms with ich & gill flukes.)
- Swimming into the flow of a powerhead (unique to velvet).
- Acting reclusive (velvet causes fish to be sensitive to light).
If
visible physical symptoms do manifest:
- Velvet may initially start out looking just like ich, with salt or sugar-like “sprinkles” visible mostly on the fins.
- Within days or sometimes just hours, these tiny white dots will spread all over the fish’s body, covering it in “dust.” This dust may look grey-gold colored if viewed at the right angle and under the right spectrum of light. For this reason, it may be difficult to see velvet on a yellow or light colored fish (look from an angle, not directly from the side). However, sometimes a fish’s body will look “dirty” or show “dark areas” just before velvet appears.
- There are two ways to differentiate velvet from ich:
- Velvet trophonts (and the correlating dots) are much smaller than ich. They range in size from 10-80 micrometers in diameter. They are also perfectly round. Ich trophonts are more oval shaped and range in size from 48 x 27 to 452 x 360 micrometers. Both start off small but then grow in size before dropping off. It has been said that velvet makes a fish look like it has been dusted with a fine powder, whereas ich is more like salt grains.
- If you can count the number of white dots on your fish, then you are probably dealing with ich. If they are too numerous to count, it is most likely velvet.
The importance of recognizing key behavioral symptoms of velvet and then beginning treatment immediately cannot be stressed enough. This is because once velvet has spread to the body, the fish is heavily infected and prognosis is bleak. However, I will demonstrate below that this is not always the case. Velvet cannot usually be managed, as ich sometimes is, due to its sheer overwhelming numbers. Survivors of velvet are usually clownfish or other fish with thick mucus coats. It is also thought a very small percentage of fish are capable of building up either natural or temporary immunity (usually 6 months max) to velvet.
Treatment options - Chloroquine phosphate is the treatment of choice for velvet, but copper also works if symptoms are caught early on. These also work on ich, so if in doubt treating with CP or copper will have you covered both ways. Tank transfer and hyposalinity
do not work with velvet. A freshwater dip and/or chemical bath (discussed in more detail below) is recommended either before or during treatment, due to the severity of this disease; however these would only provide temporary relief and will not eradicate velvet.
Fallow period - 6 weeks if you are certain it is velvet. However, if you suspect ich or any other disease(s) may be lingering in your display tank, then it is best to go fallow for 76 days.
Below is a Purple Tang with velvet. The dinospores have already attached, and have begun feeding on the fish's skin which is why he looks "dirty" in certain spots:
10 hours later excess mucous has started to build up around the insertion points, which is why you now see visible white dots. As you can see, the fish is also completely covered - another telltale sign of velvet instead of ich. This fish was dead less than 12 hrs after these pics were taken (I didn't have access to him just yet to begin treatment):
A Half Black Angelfish with velvet. Notice how it’s more difficult to see the tiny white dots on the white part of the fish’s body. This is why you must look on the fins or look from an angle, not directly from the side with lightly colored fish:
I’ve seen a tang that covered and it still be ich but here’s the item on velvet.
