Antibiotics for Fish

Updated April 17, 2017

The presence of bacteria and parasitic organisms is relatively common in both freshwater water fish and fish kept in household aquariums. The use of drugs and medications to treat these ailments is generally accepted as the most effective avenue of approach. Many of the medications used in the promotion of fish health are household names in the effort to combat disease and maintain overall wellness in the fish population.


Commonly known to veterinarians and pet-owners as Fish Mox, this widely used antibiotic is effective in the treatment and control of pseudomonas and aeromonas bacteria that commonly occur in fish. Discovered by scientists at Beecham Research Laboratories in 1972, amoxicillin is considered most effective against Gram-positive bacteria, while having some effect on Gram-negative strains.


This antibiotic is used to treat a host of bacterial infections commonly found in fish. Ampicillin was originally developed as a penicillin-type antibiotic considered effective against the spread of Gram-positive bacteria. Ampicillin or Fish Cillin, is intended for use in ornamental or aquarium fish only.


Fish Flex or cephalexin is an antibiotic that is widely used in the treatment of aquariums. Cephalexin acts by interrupting cell-wall formation in bacteria. This action will usually result in the rupture of the bacterial cell wall, reducing the ability of the bacteria to survive. For multiple pet owners, Fish Flex may also be used in the treatment of urinary tract infections, flesh wounds and ear infections in domesticated dogs. As with many of the antibiotics used in the care of fish, cephalexin may be purchased at most pet stores, at a veterinarian's office and online.


Fish Zole is an anti-parasite medication that is useful in the treatment of protozoan-based infections such as hole in the head, angle problems, Marine Ich, and Freshwater Ich in several species of fish. As a rule, Metronidazole is mostly indicated for use in aquarium and ornamental fish only. The well-known antibiotic is also seen as effective for treatment of any caught freshwater fish infected with the parasite Giardia.


Tetracycline is used in the treatment of fish ailments, such as gill disease, popeye, red pest, and tail or fin rot. Tetracycline or Fish Cycline is considered effective against Gram-negative bacterial infections. Historically, the first patent for the widely-used antibiotic was issued in 1950. Nonetheless, studies involving Egyptian mummies have indicated large amounts of tetracycline present in the bodies of the excavated ancients.

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John Marcheur is a freelance writer who began his professional career in 2010. His writing appears on a number of websites, covering a range of subjects from job search strategies to lifestyle topics and military issues. Marcheur is a military veteran who has studied marketing and small business through Pierce College in Washington.