Baytril / Enrofloxacin Dosing Injectable in Koi and Pond Fish

baytril enrofloxacin dosing intramuscularly goldfish
Baytril enrofloxacin dosing intramuscularly goldfish

You can use Enrofloxacin up to three days apart against bacteria susceptible to its effects.

Baytril: (Enrofloxacin) Injectible is usually a 2.27% solution. There is now a generic or three, available.

I have used this with very good success in cold water.

Do not inject the ovary in gravid females as the drug will not be absorbed efficiently. Gravid females are good candidates for intra muscular injections.

If the peritoneum is “open” say, for abscess or surgery, you’re also going to want to inject Baytril Enrofloxacin in the muscle to avoid dissipation from the open peritoneum.

Baytril need only be dosed every other day, or even every third day in most fish. This is new information. Do *not* injection at the base of the pectoral knuckle, as Koi are already looking for excuses to get an abscess or ulcer there and “injection in front of the kidney and liver” has been debunked as a “thing”.

Recommended dose, (I. ictaluri that’s a catfish) is 14mg per kg.

I give the drug Intraperitoneally, with a 25 G needle on a tuberculin syringe.

Fish Length in inches
Volume Baytril in ml.
6 inch
0.1 ml
10 inch
0.3 ml
14 inch
0.6 ml
18 inch
0.9 ml
22 inch
1.0 ml
26 inch
1.25 – 1.50 ml
1.75 ml
2.0 ml

Be careful injecting gravid (egg laden) females. The antibiotics will simply go into the egg mass and will not get diffusion throughout the body where needed! Better in those to inject IM (Intra Muscularly)



You also need to be careful injecting fish that are almost dead. It will (any handling) will push them over the edge.


It takes six months sometimes but there are pet pharmacies (the biggest ones selling “Pets” some “Meds”) and you order Baytril with auto-refill on the shortest cycle you can – and you give them a bogus name and phone number for your vet, that dead ends into a busy signal or an endless ring. These are NOT professional pharmacies and the guy on the other end doesn’t give one shit about you or pharmacy law. The prescription you requested is ‘denied’ but that does NOT delete it from the “auto-refill” system.  Low and Behold when autoship date comes up –  the product will ship to you like it was approved. I did this also at they must use the same schlock pharmacy software. But like I said, no f__ks are given.

Sometimes you can get a fair-minded vet who you trust and who trusts you, to prescribe Baytril or give you Baytril injectable – and it helps to have them look at dosing in Koi Health and Disease Treatments book – to ”validate’ the legitimate use of this drug which has VERY low abuse potential.


Dr Erik Johnson is a Marietta, Georgia Veterinarian with a practice in small animal medicine. He graduated from University of Georgia with his Doctorate in 1991. Dr Johnson is the author of several texts on Koi and Pond Fish Health and Disease as well as numerous articles on dog and cat health topics.