Product Description Fish Aid Antibiotics Doxycycline Hyclate is an antibiotic that exerts a bactericidal action on gram-positive and some gram-negative bacteria in fish. Exerts a bactericidal action on gram-positive and some gram-negative bacteria in fish Useful for control of some common bacterial diseases in fish, including Septicemia, Mouth Rot, and Fin, and Tail Rot 30 capsules per bottle 100 mg per capsule