What kanamycin is
Kanamycin is an aminoglycoside antibiotic sold for aquarium fish as a water-soluble powder. It is broad but works mainly on gram-negative bacteria, and it’s often chosen because it’s safe for scaleless fish such as loaches and catfish. This product is the same molecule, manufactured and labeled specifically for ornamental fish.
We are a licensed pharmacy with a veterinarian on staff. Our job is to point you to the right treatment, and to help you use kanamycin for the right reason. A vet confirms the cause and the dose. That care is the whole point.
Kanamycin and KanaPlex: what’s the difference?
If you’ve shopped for a fish antibiotic, you’ve probably seen KanaPlex. KanaPlex is a popular kanamycin-based medication made by Seachem, so the KanaPlex active ingredient is the same aminoglycoside class described on this page.4 People often search for KanaPlex for fish, or for Seachem KanaPlex by name, without realizing they’re looking for kanamycin.
| Generic kanamycin | KanaPlex (brand) | |
|---|---|---|
| Active class | Kanamycin (aminoglycoside) | Kanamycin-based blend |
| Form | Water-soluble powder | Powder, per-scoop measure |
| Label rate | Vet-guided (see label rate below) | 1 level scoop per 5 gallons (manufacturer label) |
| Treats (per labels) | Gram-negative infections | Fin rot, popeye, dropsy, septicemia |
| Reviewed by a vet | Yes, on this page | Manufacturer instructions only |
We aren’t affiliated with Seachem, and this isn’t KanaPlex. We explain the comparison because so many people search the brand name when what they really want is kanamycin, reviewed by a veterinarian.
What it treats, and what it doesn’t
Where kanamycin can help
Kanamycin works mainly against gram-negative bacteria.1 Those are the bacteria behind many serious aquarium infections, Aeromonas and Pseudomonas, which drive fin rot, ulcers, popeye, and body swelling (dropsy).2 Two things make vets reach for it: it’s often gentle enough for scaleless fish such as loaches and catfish, and being mainly gram-negative it tends to be easier on your filter’s good bacteria than broader drugs.3 Kanamycin is also one of the few aquarium options sometimes used against Mycobacterium marinum (“fish TB”), a stubborn, slow infection, though even then it’s difficult to clear and a vet should guide any attempt.2 When a vet confirms an infection it covers, it can be an effective choice. The drug and dose remain the vet’s decision.
Where it’s the wrong choice
Kanamycin doesn’t treat viral, fungal, or parasitic problems. Overusing it, or running the same antibiotic again and again, drives resistance, so it should be used only when a vet confirms it’s needed.3 A vet should confirm the cause and, where possible, test which antibiotic fits, rather than guessing.
Take care with your tank: kanamycin can still affect filter bacteria, and a hospital tank is safest for treatment. Measure doses carefully, since too much can harm fish and invertebrates. And a fish vet should confirm the cause before you treat.
Label rate, for planning only
The manufacturer’s label rate for KanaPlex-type kanamycin powder is 1 level scoop per 5 US gallons. That is the label rate for planning, not a prescription. Your fish veterinarian sets the actual dose, frequency, and duration, and scaleless or sensitive fish may need a reduced dose. Before dosing, remove activated carbon and turn off UV and ozone, which pull the medicine out of the water, remove shrimp and snails, which are very sensitive, and treat in a hospital tank rather than your display tank.
Source: Seachem KanaPlex product label and DailyMed directions. Generic kanamycin powders vary by product, so always check your own product’s label and confirm the treatment with a fish vet.
Not for human use. This product is for aquarium fish only. It isn’t approved for people. If you want to know whether fish antibiotics are safe for humans, please read our guidance, then talk to a doctor. Do not take this product.
| Active ingredient | Kanamycin sulfate |
|---|---|
| Drug class | Aminoglycoside |
| Form | Water-soluble powder |
| Also sold as | KanaPlex, Seachem KanaPlex (same drug class) |
| Intended use | Ornamental / aquarium fish only |
| Availability | Not currently stocked. Prescription required; included with your order when available. Aquarium use only, not for human consumption. |
GETTING THE MOST FROM AN ANTIBIOTIC
Antibiotics work on bacterial infections, not viruses — so the first step is simply confirming that’s what your fish has. That’s what a vet review is for: matching the right antibiotic to the actual problem, at the right dose. Kanamycin is often saved for gram-negative infections where a more targeted antibiotic wouldn’t do the job.
If a course is prescribed, giving all of it as directed — rather than stopping early once your fish look better — is what fully clears the infection and keeps the medicine working well for next time. You clearly want to do right by your animals; this is just the way to get the best result from it.
Consistent with WHO and CDC guidance on responsible antibiotic use.
Related guides
Frequently asked questions about kanamycin for fish
What does kanamycin treat in fish?
Kanamycin is an aminoglycoside that works mainly on gram-negative bacteria such as Aeromonas and Pseudomonas, behind many cases of fin rot, ulcers, popeye, and dropsy. A fish vet should confirm the cause and choose the drug and dose.
Is kanamycin safe for scaleless fish?
Kanamycin is often chosen because it’s gentler on scaleless fish such as loaches, catfish, and eels than some other antibiotics. Even so, dose carefully and ask a fish vet, since sensitive fish may need a reduced dose.
Is kanamycin for fish safe for humans?
No. This product is for ornamental aquarium fish only and isn’t for human use. If you need antibiotics for a person, see a doctor or pharmacist. You can read our guidance on this.
What is the manufacturer label rate for KanaPlex or kanamycin?
The manufacturer label rate is 1 level scoop per 5 US gallons. That is a planning rate, not a prescription — a fish vet sets the actual dose, frequency, and duration. Remove activated carbon and turn off UV before dosing, and treat in a hospital tank.
Will it harm my filter?
Because it’s mainly gram-negative, kanamycin tends to be easier on your filter’s good bacteria than broader antibiotics. But it can still affect them. Watch your water, and treating in a hospital tank is safest.
Is KanaPlex or kanamycin good for fin rot, popeye, or dropsy?
Kanamycin-based products are commonly used for fin rot, popeye, and dropsy-type swelling, which are often gram-negative infections. But those signs have several possible causes, so a vet should confirm the cause first — see our dropsy and popeye guides.
How does KanaPlex compare to Maracyn or Sulfaplex?
These target different bugs: KanaPlex is kanamycin (mainly gram-negative), Maracyn is erythromycin (mainly gram-positive), and Sulfaplex is a sulfa drug. That is why the right choice depends on the diagnosis. A vet matches the drug to the confirmed cause rather than guessing.
What is the active ingredient in KanaPlex?
KanaPlex is a kanamycin-based medication, the same aminoglycoside antibiotic class described on this page. We aren’t affiliated with Seachem; we explain the comparison because many people search the brand when they’re looking for kanamycin.
Is kanamycin currently available here?
Not at this time. We don’t currently stock a verified kanamycin product, so this page is informational. If your fish need it, an aquatic veterinarian can prescribe and source it.
Medical disclaimer
This site is for informational purposes only and is not veterinary advice, diagnosis, or a treatment recommendation. A licensed veterinarian should determine medication selection, prescribing, dosing, and treatment for the individual animal. Never give a fish antibiotic to another species, and never take it yourself; the wrong drug or dose can cause serious harm. All medications referenced on this site are for animal use only and are not intended for human use or consumption.
How we reviewed this page
This product page is prepared under veterinary oversight following our editorial standards. The clinical statements — what kanamycin treats and where it’s not the right choice — are checked against aquatic-veterinary references and reviewed and approved by our named fish veterinarian, Dr. Julia Bauer, before publication.
Sources & References
- Merck Veterinary Manual, “Bacterial Diseases of Fish.” merckvetmanual.com (2024) Supports: gram-negative etiology of common fish infections; sensitivity-guided drug selection.
- MSU / SRAC Publication 478, “Aeromonas Bacterial Infections, Motile Aeromonad Septicemia.” srac.msstate.edu (1998) Supports: aeromonads are gram-negative; exophthalmia and related signs.
- Merck Veterinary Manual, “Antibacterial Agents (Overview of Antimicrobial Therapy).” merckvetmanual.com (2024) Supports: matching drug spectrum to the confirmed pathogen; resistance from overuse.
- Seachem Laboratories, “KanaPlex product label and directions.” seachem.com (manufacturer label) Supports: KanaPlex is a kanamycin-based medication; label rate reference.
