Brooklynella Hostilis
This parasite infection is commonly known as "Clownfish Disease", because it is so frequently a problem with clownfish, especially wild-caught ones. Although it is seen most often in clownfish, other types of fish can suffer from infection. Symptoms are usually noticed on only one or two fish to begin with, but it can spread rapidly. Brooklynella hostilis is fast acting and can kill in just a couple of days if left unchecked. Can easily be confused with Marine Velvet.

Visible symptoms are the following:
• Increased mucus production
• Loss of appetite
• Turbidity of the skin
• String-like material hanging from the fish
• Increased respiration, or even open-mouth gasping
• Hyperactivity in early stages
• Cloudy eyes associated with secondary bacterial infections
• Faded colors or discolored areas
• Hanging at the surface or laying on the bottom in late stages of infection
• Rapid weight loss associated with dehydration, as fish lose their ability
to osmoregulate.
• Loose scales
• Secondary bacterial infections



What causes brooklynellosis?
Brooklynellosis is caused by a ciliated protozoan known as Brooklynella hostilis Lom and Nigrelli, 1970. B. hostilis is found pretty much all over the world, but is more common in warmer waters (Lom, 1995). It infects most marine teleosts (bony fishes) but has not been detected in wild fish (Lom, 1995). Brooklynella has no free-living stages (Lom, 1995).
The parasite attacks the gills of the infected fish and with heavy infections, the surface tissue of the gills is destroyed and the parasites feed on tissue debris and ingest blood cells (Lom, 1995).

The signs of brooklynellosis
As the parasite causes respiratory difficulties, the infected fish show rapid or labored breathing and may swim close to the water surface in an attempt to get sufficient oxygen. The gills may hemorrhage and small red spots may be present. A heavy infections will usually cause the death of the fish. Skin lesions are also often associated with brooklynellosis.

Prevention of brooklynellosis
Quarantining a fish for a number of weeks before it is moved to a display tank will allow you to observation it for signs of disease or parasites.

Treatment of brooklynellosis

Formalin Baths
Formalin baths for 30 to 60 minutes, or as long as the fish can take it. The bath water should be matched closely with the tank water and probably the best way is to take water from the tank and place it in a bucket, add the formalin, mix well, and treat the fish. Add an air stone to the bucket to ensure good aeration (and then toss the air stone away). After the dip is completed, dilute the dip water with tap water and discard it, also discard the bucket too. Have a second bucket of tank water ready to transfer the fish to when the treatment is complete or if the fish starts to show signs of stress. The second bucket allows the fish to be "rinsed" before it is placed back into the tank, as you don't want to get formalin in your display tank. If the fish appears to be having trouble breathing, more than before the bath started, remove it at once.

The dosage should be for each gallon of water, around 0.6 ML of formalin should be added to get the desired dosage. The warmer your water, the less formalin that should be used as both formalin and increasing temperature reduces the oxygen saturation of the water. You should use formalin 37.5%.

Formalin is very dangerous and care should be taken when using it. Gloves and eye wear should be used, and disposed of when done. If you do get any on yourself it should be rinse off right away.