Polypterus senegalus diseased (bichir)

[aqualifestyle34]

polypterus senegalus diseased symptoms: white spots (discoloration of skin), no foam appears normal behavior and good food (earthworms) other fish have no symptoms, no treatment being chemical in tank and food and healthy is very good.
what is the disease that gives white spots?
Can you advise me on treatment?

[aqualifestyle34]

hello friends, this is not my fish to my friend I told you the information as needed.
stains measures 5 to 8 mm in diameter the size of polypterus and 7 to 9 cm, it is not stain granular (no thickness), they are internal, the appearance gives a slight bluish tint. We doubt that the callabaricus who died before would be the carrier of the disease, the two bichir are purchased in two different stores. We thought of treatment with salt for 45 minutes 15 to 25 grams per liter and after a change of course change aquarium water for the full course polyptérus acclimation to drip.
For the aquarium 300 liters contaminated my friend will use his diatom filter micron filter to remove all traces of bacteria and other ...

for the pictures I think that tomorrow he can do.
ps: my friend is not very good at computer otherwise it would be with us especially with 37 years of aquarist.
Me and him we have never seen this disease.