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Marine velvet is one of the most common illnesses in marine fish.

Marine velvet attacks fish in all different types of saltwater tanks from

reef tanks to species tanks. Marine velvet is common in wild caught

fish. The disease can affects healthy fish only if they are kept with

infected fish or if something radical happens.

Symptoms:

In most cases the gills are damaged first, the fish will be in

extreme distress and respiration will increase significantly so gasping

for air is a common behavior in this cases.  The second symptom to

appear is dusting or powdering on the fish body. To be accurate the

dusty appearance is multiple micro whitish dots.  Another common

symptom is when the fish is infected it will refuse to eat.

The fourth symptom that can be noticed is when the fins are close to its body along brushing its body

against rocks and substrate. 

Life Cycle:

The marine velvet parasite has two life stages:

1-   Free-swimming stage, in this stage the fish is actually gets infected.  The parasite moves itself

through the water and keeps floating until it find its host to attach to. In most scenarios it will attach

itself to the gills and to the skin. After attaching it will forms a cyst.

2-    Cyst form, the cyst form is the stage when the parasite start to reproduce. Like in many diseases

when there is a cyst form the cyst falls off of the fish and start the reproduction stage by cell division.

After 3-4 days there are hundreds of new free-swimming parasites looking for a host.

Treatment:

There are several methods to threat marine velvet. Here are some effective and common treatments for

marine velvet:

1-    To move infected fish to a hospital fish tank, the salinity should be lowered in the hospital tank; the

parasites can not survive low salinity and die fairly fast. The problem with this method is that it can be

a hard task to reintroduce the fish to higher salinity levels 

2-    Using chemical treatments for the marine velvet disease include using copper. Make sure to carefully

follow the instructions provided by the manufacturer. The problem with this method is to use it in reef

systems, moving infected fish to the hospital tank can be good idea.  

3-    Freshwater dip, freshwater dip should be last for 3 minutes, this action eliminate most of the

trophonts on an infected fish. Unfortunately this method is not 100% effective but it sure gives an

infected fish some relief by eliminating some of its parasites. This method can be used parallel to

other treatment.  

4-   Hyposalinity- Hypo means "lower than normal". The term Hyposalinity is actually lower amount of

salt contained in saltwater than normal. This method occurs when we bring the salt content down to a

range of 1.012 to 1.010 ppm. The parasites can not survive low salinity and die very fast.