Saltwater Ich and Velvet

by Kevin Kohen on January 7, 2010

Male Ventralis Anthias

Male Ventralis Anthias

After diving into the wonderful world of keeping saltwater or marine fish, most everyone eventually encounters some form of disease associated with marine fishes.  Understanding how to properly medicate and condition fish to boost their immune system is one way to ensure you are providing the best possible care for piscine friends that we so lovingly care for in our homes.

Two of the most common ailments that affect marine fishes are Amyloodinium ocellatum (Marine Velvet) and Cryptocaryon irritans (Saltwater Ich).

Having been an avid marine aquarist for decades, I have gained valuable experience over the years in dealing with most ailments that can affect fishes.  One of the most common questions I am asked is:  Why do my fish seem to break out with Marine Velvet or Ich immediately after I finish treating them?

More often than not this can be attributed to either the duration of the treatment period is for too short of a time frame, the incorrect medication or ineffective medication are being administered, or the dosages are too low during the treatment period.

First and most important, I only recommend medicating fishes in a quarantine aquarium, outside of the display aquarium.  Most medications are extremely toxic to invertebrates, and some can kill beneficial nitrifying bacteria that breaks down the waste produced by the animals in the display.  The quarantine aquarium should be filtered with an established bio-filter to keep the water parameters within acceptable ranges during the treatment period.  This can be accomplished by always running a sponge filter or small hang- on power filter in the sump of the display aquarium.  When the time arises, this well established filter can be pulled from the sump and utilized in the quarantine aquarium.

Prognathodes guyanensis var

Prognathodes guyanensis var

Normally at a temperature of 78 degrees, treatment for Marine Velvet or Saltwater Ich should be performed for a minimum of 10-14 days.  The use of ionic Copper Sulfate maintained consistently at 0.15-0.20 ppm, tested with a good quality Copper test kit, in conjunction with Formalin (1ml/100l per day) is proven  effective in killing both of these more common ailments.  Use caution when treating fish such as Centropyge spp., Cirrhilabrus spp., and Paracheilinus spp. to name a few, as they are very sensitive to elevated copper levels above 0.15 ppm.

The life cycle of these parasites is very interesting.  Once you actually see visible signs of the disease, they are at the end of their life cycle.  The white spots (Marine Ich) or the appearance of what looks like someone dumped baby powder over the fish (Marine Velvet) are called tomites, and they will soon fall off of the fishes’ body and lay dormant for several days in the aquarium.  Within a few days (temperature dependent) the microscopic parasites will then hatch out and swim around the aquarium until they are able to find a host fish again, parking themselves first in the gills of the host fish, then eventually on the fins and skin where they begin to grow in size, eventually becoming visible to the naked eye.  The only time medication is effective at killing these nasty pests is during the time they hatch out from their dormant period prior to them harboring on your favorite fishes. If the tomites are unable to find a suitable host fish, they will quickly perish within 24-48 hours.

After properly treating your finned friends, eliminating as many stressors as possible is the first course of action to ensure their survival.  Aggression or harassment from existing tankmates should be avoided as this can be very stressful to newly introduced fish.  Additionally, avoiding exposure to very intense lighting for the first 24-48 hours is also important, as well as making sure the water temperature does not fluctuate more than 1 degree per day is another great way to eliminate stress.  Lastly, don’t forget about water chemistry; keeping the water pristine as possible, making sure your beloved fish are not exposed to low pH conditions, elevated ammonia, nitrite, or nitrates levels, will all help to ensure they make a complete and successful recovery, and regain their strength and settle in well in the display aquarium.

Nutrition is another key factor in keeping your fish healthy, or boosting their immune system to make a speedy recovery after being treated for a specific ailment.  Not all of the foods we feed our fish have enough or the correct combination of vitamins, trace elements/minerals, or amino acids so some form of enrichment is very beneficial.  Enriching the foods we feed our finned friends every day is a very important factor in conditioning new fish, preventing disease, and just plain keeping your fish healthy.

I have had the best results with inoculating freshly thawed and drained frozen foods on a daily basis with a good quality supplement such as:

Happy fishkeeping!

Kevin Kohen


About the author: Kevin earned his Bachelor of Science degree from Wright State University, and is an avid marine life photographer, lifelong aquarist, and marine fish enthusiast. He has worked in the aquarium industry since 1983. He launched the LiveAquaria.com web site in 2000 and designed and oversaw the installation of the Drs. Foster and Smith Aquaculture Coral and Marine Life Facility, which opened in July of 2005. Kevin is currently the Director of LiveAquaria at Drs. Foster and Smith. See more articles by Kevin Kohen.

{ 2 comments… read them below or add one }

Felicia January 7, 2010 at 4:53 pm

Wow, thanks for this extremely informative article. This answers all the common questions about Ich and marine velvet.

I love the photo of the yawning Anthias, too!

dog grooming business May 13, 2010 at 1:10 pm

Thanks for the tip about the treatment duration period. I had never heard of that but it really explains much. This article is great – I’m going to give it a quick re-read to make sure I absorb everything.

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