Symptoms: Small black spots which appear on the skin surface.  In areas of a puffer with little pigment, the spots may be yellowish instead of black.

Treatment: Black spot is easily treated with a chemical known as formalin.  Use that which you would find in your LFS, and check the label for dosage.  Salt baths have been known to be effective as well. Formalin is a known carcinogen.  If you are going to be using this chemical, check the Puffernet Rx for data on formalin.  Use half the recommended dose, as puffers are sensitive to this medication.

Background: Basically a cold-water parasite, the visible spots contain a light-colored cyst of binding tissue in which a slowly moving worm lies rolled up. The cyst is surrounded by an accumulation of pigment cells, which causes the "Black-spot" to be seen from the outside.  The worm in the cyst is a larval stage of a sucking worm, Neodiplostomum cuticola. The adult parasite lives in the intestines of water birds. The eggs reach the water with the excretal of the bird, where they hatch.   A parallel life history takes place in aquatic snails.