Antibiotic treatment

What It Treats – Bacterial infections, which are oftentimes “secondary” to preexisting parasitic (and worm) infestations.

How To TreatFollow the directions on the label of whatever product you are using. Always use a broad spectrum antibiotic medication i.e. one that treats both gram-positive and gram-negative bacterial diseases.

The following are medications I recommend (in order of preference):

1) Ciprofloxacin (Best administered via 1-2 hour bath treatment. Dosage is high: 250mg per gal. Repeat every 24 hours for 7 days. Methylene Blue can be added to increase efficacy.)

2) Enrofloxacin (Most advanced antibiotic approved for use in tropical fish … Dosage range is 2.5 – 5 mg/L daily for 7 days; can be used both in a QT or as a 5 hour bath treatment. The tricky thing about Enrofloxacin is the 2.5 – 5 mg/L dosage range is actually safe for QT use, but the nitrifying bacteria will also take a hit. So, the primary reason to administer the medication as a 5 hr bath is to spare your biofilter.)

3) Nitrofuracin Green Powder (Best used in a QT with no working biofilter, as the Methylene Blue contained therein can destroy nitrifying bacteria.)

** NFG (Nitrofuracin Green) contains: Nitrofurazone*, Sulfathiazole Sodium, Methylene Blue. The efficacy of NFG can be reproduced just by dosing Methylene Blue, Furan-2 and Seachem Sulfaplex all together. For a 30 minute bath, I recommend dosing methylene blue @ 1 ml per gallon and double dosing both of the antibiotics. For in-tank dosing, I recommend using methylene blue at 1 teaspoon (5 ml) per 10 gallons and dosing both antibiotics as directed on their respective labels. Repeat every 24 hours with a 25% water change before each treatment. Treat for 10 – 14 days.

4) AAP Spectrogram (Kanamycin/Nitrofurazone* synergistic combination … Can be combined with Metronidazole … Can be safely used in a QT with a working biofilter.)

5) Furan-2 (which contains Nitrofurazone*) + Seachem Kanaplex + Metroplex (metronidazole) – Can be used separately, but most effective when all 3 are combined together. Furan-2 + Kanaplex should be dosed at the same time for maximum effectiveness. Can be used in a QT with a working biofilter.

6) Triple Sulfa Powder

7) Seachem Sulfaplex + Neoplex (Can be used separately or together.)

8) Maracyn 1 (Erythromycin) – Best antibiotic for treating eye infections.

When using antibiotics, it is very important to treat for 7 – 10 consecutive days. Follow the instructions on the label – which may say to dose every 24 or 48 hours, do water changes, etc. But use the product for 7 – 10 continuous days (as directed). Sometimes a fish will look & act better after just a few days of treatment; however the infection can return if you end treatment prematurely. Or sometimes the opposite will happen, as antibiotics can be notoriously slow acting with fish. If a fish shows no signs of improvement after 10 days, then it’s time to try a completely different medication. Just like with humans, sometimes a certain fish will respond better to a different treatment.

Another option for using antibiotics is daily baths. Most antibiotics can be double dosed in a 30 minute bath treatment. Aerate the bath for at least 30 minutes prior and maintain aeration + temperature throughout.

The medications listed above are primarily meant to be dosed into the water. Using antibiotics in a QT environment (or bath treatment) fits within the comfort level of most hobbyists. However, the best way to apply antibiotics is via intramuscular injection (obviously difficult to do with small fish). The first step is to sedate the fish using MS-222 (Tricaine Methanesulfonate). Next, inject an antibiotic (e.g. enrofloxacin), or a steroid such as dexamethasone to help reduce inflammation/swelling. The injection is made into the muscle on the side of the dorsal ridge, angling the needle towards the head or tail to avoid hitting any major organs below. Typically you would use a tuberculin syringe with a 27 gauge needle to draw up the solution and a 30 gauge needle to inject. After the injection is complete, place the fish in a heavily oxygenated bucket with clean saltwater and glide the fish through the water until he is revived. Dosage for Intramuscular dexamethasone varies from 1-2 mg/kg. Dosing info for enrofloxacin and other fish antibiotics can be found here.

You can also food soak antibiotics; this is especially useful for treating internal infections. Neomycin (e.g. Neoplex) will not get absorbed by the fish’s gastrointestinal tract, thus making it an excellent antibiotic to soak in food. I’ve also had success using kanamycin (e.g. Kanaplex) to treat internal infections. Metronidazole (e.g. Metroplex) is another good option and can also be used to treat internal flagellates. See Table 1 (here) for other ABX which can be soaked in food. It is also important to use a binder to greatly reduce the loss of medication to the water through diffusion (this also makes food soaking reef safe). Seachem Focus, unflavored gelatin or agar are all examples of binding agents that can be used. My recipe for food soaking ABX can be found below:

Using a shot glass:
1 tbsp food (preferably pellets or frozen food)
1 scoop (~ 1/8 teaspoon) of medication
1 scoop Focus
A few drops of saltwater or fish vitamins
Stir until a medicated food slurry has been achieved
Feed after soaking for 30 mins
Refrigerate or freeze any leftovers for future use

ProsCan be mixed with other medications; however effectiveness may be limited if used in the presence of an immunosuppressant (e.g. copper, Chloroquine).

Cons/Side EffectsSuppresses appetite, depletes the water of oxygen (so provide additional gas exchange). Antibiotics dosed in water are notoriously slow acting in fish.

Further reading below:

* Nitrofurazone is carcinogenic