Keep your ornamental fish happy and healthy with Fish Pen, an antibiotic that exerts a bactericidal action on gram positive and some gram negative bacteria. Common fish diseases that it is good for include fin and tail rot and flexibacter infections. Each tablet contains 250 mg of penicillin and, even though the same USP grade is given to it, it is not labelled for human consumption. This should not be used for food fish. This is a 30-count bottle.