Fungus - Saprolegnia fish disease

Fungus - Saprolegnia fish disease

1. General description

Fungus-like protists (which are caused this disease) are aquatic forms of saprotrophic organisms (saprobes). These are organisms which acquire nutrients from dead or decayed organic matter (death fish or other animals, metabolic waste, remnants of food on the bottom of aquarium etc.). They attack only health but weakened fish or fish with damaged skin tissue because of injuries, wounds, bacterial infections or parasitic infections.

The fungi secrete digestive enzymes which dissolve host tissues and cells. The fungi absorb proteins and carbohydrates which are degradation products. This is the reason why late detected/diagnosed of the disease can be deathly. Then infected gills cause suffocation of the fish.

The fungus-like protists reproduce by releasing of thousands spores to the water. These spores always are in water reservoirs, also in aquariums and we can't eliminate them.

2. Type of the disease

This is a fungal disease.

3. Cause of the disease

Causes of this disease are fungus-like protists from Saprolegniaceae family.

4. Favorable circumstances for development of the disease

• low water temperature
• poor water quality
• injuries, wounds, earlier bacterial or parasitic infections – this disease attacks only damaged tissues
• weakened fish

5. Common symptoms of the disease

• feathery clumps of whitish or brown/gray mycelium, which looks like cotton develop on the fish skin, in earlier damaged areas
• initially small outbreaks spread quickly through whole body and gills
• rubbing
• the fish almost stop their activity
• infected roe is covered by white lint

6. Types of the treatment

We need eliminate main reason of the disease and next we should do 50% partial water change, increase water temperature and increase oxygen saturation before treatment.

6.1. Brushing

Treatment consists of washing infected areas with help of cotton wool pad or stick. So we put sick fish on a wet cloth/tea-towel and we brushing the infected areas. When fish start suspiciously to behave we must put back it in aquarium. We need avoid hand touch. We use for brushing potassium permanganate solution (we dose 1g per 1 litre of the water) or iodine (we dose 1ml per 10ml of the water).

6.2. Medicinal baths

Short-term in a separate aquarium:

• sea salt – we dissolve salt in the water (15g per every litre of the water), bath should last about 30 minutes, we may repeat this bath until all disease symptoms stopped;
• potassium permanganate – we dose 0.5g per every 10 litres of the water, bath should last about 10 minutes, we may repeat the bath 2-3 times per week until all disease symptoms stopped.

Long-term:

• Zoolek FMC preparation – we dose 10ml per every 100 litres of the water, after week we add half dose;
• Zoolek Aquasan-S preparation – we dissolve 1 capsule in 50 litres of the water.

7. Comments about this disease

• This disease attacks only weakened, sick or injured fish.
• This disease is secondary infection – it doesn't attack health fish.
• This disease is dangerous because of it very quickly spread on the fish body.
• Symptoms of this disease are similar to symptoms of mouth fungus disease. So we need properly diagnose both diseases.

8. Prevention

• adequate water parameters in aquarium, especially water temperature and water pH
• avoiding mechanical injuries
• prevention of fish illness