Fin Mox Doxycycline 100 mg Fish Aid Antibiotics contains doxycycline hyclate and is formulated to help control certain bacterial infections in fish. This antibiotic works by exerting a bactericidal effect on gram positive and some gram negative bacteria that commonly affect aquarium and pond fish. It may be useful in the management of common bacterial diseases such as septicemia mouth rot and fin and tail rot. Each bottle contains 30 capsules with 100 mg of doxycycline per capsule providing a convenient option for fish health treatment when used as directed.