Velvet disease, also known as marine velvet or Amyloodinium ocellatum, is a highly contagious and often fatal parasitic infection in saltwater fish. It is a condition that every aquarist should know about to protect their aquatic ecosystem. Here’s everything you need to know about velvet, from its causes to how to identify and treat it.
What is Velvet Disease?
Velvet disease is caused by a dinoflagellate parasite that attaches to fish, forming a fine, dusty coating on their skin. This parasite can infect the gills, skin, and fins, leading to difficulty breathing, loss of appetite, and ultimately death if left untreated. The disease progresses quickly, so early detection is key.
What Causes Velvet Disease?
The parasite thrives in tanks where fish are stressed. Factors like poor water quality, rapid changes in temperature or salinity, overcrowding, or introducing an infected fish without proper quarantine can trigger an outbreak. Stress compromises a fish’s immune system, making it an easy target for the parasite.
The Life Cycle of the Parasite
The parasite has a three-stage life cycle that enables it to spread rapidly:
- Trophont Stage: The parasite attaches to the fish, feeding on its skin and gills. This is when the symptoms become noticeable.
- Tomont Stage: It detaches and settles on surfaces in the aquarium, forming a cyst that protects it while it multiplies.
- Dinospore Stage: The cyst releases free-swimming dinospores into the water, which seek out new hosts.
Each stage makes the parasite harder to control, especially in an unprepared tank.
Symptoms of Velvet Disease
Velvet is characterized by a distinctive gold or rust-colored coating on the fish’s skin that resembles velvet. Other signs include:
- Labored breathing or rapid gill movement
- Lethargy or unusual swimming behavior, such as staying near the surface
- Flashing (scraping against surfaces)
- Loss of appetite or refusal to eat
Early recognition of these symptoms can mean the difference between saving your fish and losing them.
Velvet vs. Ich: How to Tell the Difference
Velvet and ich (white spot disease) are often confused, but there are key differences. While ich produces larger white spots, velvet’s spots are much finer and have a golden or rust-like sheen. Velvet progresses much more aggressively than ich, and without treatment, infected fish can die within a few days.
What Happens if Your Fish Get Velvet?
If untreated, velvet can lead to respiratory failure, secondary infections, and death. The parasite damages the fish’s gills, making it difficult for them to extract oxygen from the water. Over time, the stress and damage caused by the parasite overwhelm the fish’s immune system.
How to Treat Velvet Disease
Acting quickly is critical when velvet is detected. Here are the key steps to take:
- Isolate Infected Fish: Move affected fish to a quarantine tank to prevent the spread of the parasite.
- Use Medications: Treat with copper-based medications or other velvet-specific treatments. Follow the instructions carefully, as copper can harm invertebrates and live rock.
- Dim the Lights: Velvet parasites rely on light for photosynthesis during their free-swimming stage. Reducing the light levels in your tank can help slow their reproduction.
- Improve Water Quality: Test and adjust water parameters to ensure optimal conditions for your fish. Clean, stable water reduces stress and supports recovery.
- Freshwater Dip: A short freshwater bath can help remove some parasites from an infected fish. However, this should only be used in combination with other treatments.
Preventing Velvet Disease
Preventing velvet is much easier than treating it. To avoid outbreaks, take these precautions:
- Quarantine new fish for at least two weeks before adding them to your main tank.
- Maintain stable water conditions by regularly testing and adjusting parameters.
- Avoid overcrowding and minimize stressors like sudden temperature changes.
By taking these steps, you can create a safer and healthier environment for your fish.
Velvet disease is a serious threat to saltwater aquariums, but with vigilance and prompt action, it can be managed.