Aquarium fish antibiotics
Kanamycin for Fish: Aquarium Kanamycin Sulfate Powder
A broad, mainly gram-negative aminoglycoside for ornamental fish, suitable for scaleless species. Intended for aquarium fish only, not for human use.
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Delivery in 10–14+ business days. Restock your aquarium’s medicine shelf before your fish need it. This is for planning ahead, not same-day treatment.
No public checkout. After you place an order, our pharmacy confirms your address and sends a secure payment link. A qualified team member reviews every order for aquarium use before it ships. Your card isn’t charged until you approve the link.
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Quick answer: Kanamycin is an aminoglycoside antibiotic for aquarium fish. It is broad but works mainly on gram-negative bacteria such as Aeromonas and Pseudomonas, behind many cases of fin rot, ulcers, popeye, and dropsy. It is the active-class ingredient in popular branded products, so KanaPlex is a kanamycin-based medication. Use the dosing calculator below to scale the label dose to your tank. A fish vet should confirm the cause; drug choice and dose are the vet’s call. For aquarium fish only; not for human use.
Not sure of your tank size? Use our free aquarium tank volume calculator to get the true water volume for accurate dosing.
Starting a course? Use our antibiotic treatment tracker to log each dose, stay on schedule, and know when it’s time to call the vet.
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, vet-staffed pharmacy, not a repackager. Our job is to sell you 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 dose | Vet-guided; see calculator | 1 level scoop per 5 gallons |
| 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.
How to use KanaPlex and kanamycin: dosage, instructions, and directions
The most common question is simple: how much do you use? The label directions are 1 level scoop per 5 US gallons, but few tanks are exactly 5 gallons. So the calculator below scales the KanaPlex dosage to your tank. It gives the manufacturer’s instructions, not a prescription; a fish vet should confirm the treatment.
KanaPlex & kanamycin dosing calculator
Enter your tank size to scale the manufacturer’s label dose. This shows the label instructions. It isn’t a prescription, and a fish vet should confirm treatment.
- Schedule: one dose every 48 hours, up to a maximum of 3 doses.
- Before dosing: remove activated carbon and turn off UV and ozone, they pull the medicine out of the water.
- Invertebrates: remove shrimp and snails; they’re very sensitive.
Source: Seachem KanaPlex product label and DailyMed directions (1 level measure per 5 US gallons, every 48 hours, maximum 3 doses). Generic kanamycin powders vary by product, always check your own product’s label and confirm with a fish vet.
| Active ingredient | Kanamycin sulfate |
|---|---|
| Form | Water-soluble powder |
| Pack size | Treats 200 or 1,000 gallons |
| Drug class | Aminoglycoside |
| Form | Capsules sealed in blister packs, open for tank dosing |
| Intended use | Ornamental / aquarium fish only |
| Availability | Over-the-counter for aquarium use only, not for human consumption |
| Delivery to | Free to all 50 US states & Canada, other countries, contact us |
Why blister packs, not a bottle
Each capsule is sealed in its own aluminum foil pocket, backed by foil on both sides. That keeps every dose away from moisture and light until you use it. This matters for kanamycin powder, which is sensitive to moisture.
Pre-measured sachets are different from one big tub. Each sealed dose stays dry until you use it. Sealed pockets also make tampering easy to see, and U.S. regulators count blister packs as tamper-evident. Blister packs cost us more than bulk bottles. The protection is worth it.
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.
Not for human use. This product is for aquarium fish only. It isn’t approved for people. Do you want to know if fish antibiotics are safe for humans? Please read our guidance. Then talk to a doctor. Do not take this product.
How your order is reviewed and shipped
Add the quantity you need to the cart (1–12). Instead of a public checkout, our pharmacy emails you to confirm your delivery address and send a secure payment link. Nothing ships until that review is complete. It is how a vet-staffed operation keeps eyes on every order and confirms it’s intended for appropriate aquarium use. We email you at each step, reserved, confirmed, payment link sent, paid, and shipped. So you never have to sit and refresh a page.
GETTING THE MOST FROM AN ANTIBIOTIC
Antibiotics work on bacterial infections, not viruses — so the first step is simply confirming that’s what your pet has. That’s what the vet review here is for: matching the right antibiotic to the actual problem, at the right dose. This one is broad-spectrum, so a vet will typically save it for 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 pet looks better — is what fully clears the infection and keeps the medicine working well for next time. You clearly want to do right by your animal; this is just the way to get the best result from it.
Consistent with WHO and CDC guidance on responsible antibiotic use.
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.
Do I need a prescription?
This is an over-the-counter product for aquarium use. After you add it to the cart, our pharmacy confirms your delivery details and sends a secure payment link before anything ships.
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.
How do you dose KanaPlex or kanamycin per gallon?
The manufacturer label rate is 1 level scoop per 5 US gallons, every 48 hours, up to 3 doses. For other tank sizes, use the dosing calculator above to scale it. Remove carbon and turn off UV first, and confirm treatment with a fish vet.
How much KanaPlex for a 1-gallon betta tank?
At the label rate, a 1 US-gallon tank works out to about a quarter scoop, hard to measure by eye, which is why the calculator rounds to the nearest measurable amount. For a small betta tank, ask a fish vet about a safe, measurable dose rather than guessing.
Is KanaPlex or kanamycin good for fin rot, popeye, or dropsy?
KanaPlex for fin rot is one of the most common uses, and kanamycin-based products are also used for popeye and dropsy-type swelling, all 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.
Can I use KanaPlex for a betta?
KanaPlex for betta is common, but betta tanks are usually small (1–5 gallons), so scaling the dose matters, use the calculator and round to a measurable amount. Bettas are hardy but small, so confirm the dose with a fish vet before treating.
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.
Does kanamycin for fish wipe out my biological filter?
It can affect it. Because kanamycin for fish is a strong, broad aminoglycoside, dosing it in a display tank can knock back the beneficial bacteria in your filter, which is why hobbyists warn about it and why treating in a separate hospital tank is safest. Monitor ammonia and nitrite closely if you must treat in the main tank.
Related guides
Fish dropsy. A gram-negative infection where kanamycin is one of the drugs a vet may choose.
Fin rot. A common gram-negative infection kanamycin is frequently chosen for once a vet confirms it.
Columnaris. The fast cotton-wool disease where a gram-negative-active drug like kanamycin may fit.
Fish popeye. The bulging-eye sign, its causes, and when antibiotics help.
Are fish antibiotics safe for humans?. A clear, no-sales answer.
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.
