Aquarium fish antibiotics
Fish Mox: Aquarium Amoxicillin 250 mg Capsules (100 Count)
Broad antibiotic for ornamental fish, 250 mg. Intended for aquarium fish only, not for human use.
These images are for illustrative purposes only.
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.
New here? See how our free vet prescription works. You pay only for the medication; a licensed vet must approve it first. A licensed vet reviews every order, with no separate consult fee.
Quick answer: Fish mox is amoxicillin for aquarium fish. It helps with some bacterial infections, mainly gram-positive or mixed infections a vet has identified. It is a poor match for the gram-negative infections behind dropsy and popeye. 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 fish mox is
Fish mox is the common name for amoxicillin sold for aquarium fish. Amoxicillin is an aminopenicillin, a broad, widely used antibiotic that physicians and veterinarians both prescribe. This product is the same molecule, manufactured and labeled specifically for ornamental fish.
We’re a licensed, vet-staffed pharmacy, not a repackager. Our job’s to sell you the right treatment, and to tell you plainly when amoxicillin is the wrong choice for your fish. That candor is the whole point.
| Active ingredient | Amoxicillin trihydrate |
|---|---|
| Strength | 250 mg per capsule |
| Count | 100 capsules |
| Drug class | Aminopenicillin (beta-lactam) |
| 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. It matters for amoxicillin, which is sensitive to moisture.
A bottle is different. Every time you open it, the capsules still inside meet air and humidity again. 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 amoxicillin can help
Amoxicillin is broad-spectrum, and it treats some bacterial infections in fish, mostly the gram-positive or mixed infections a fish veterinarian has identified. When a vet confirms an infection it covers, it can be an effective choice. The specific drug and dose remain the vet’s decision, guided by testing.
Where it’s often the wrong choice
Many sites push amoxicillin (“fish mox”) for almost any sick fish. But dropsy, popeye, and many ulcers are caused by gram-negative bacteria, which amoxicillin matches poorly, these organisms often shrug it off. If your fish shows those signs, ask a veterinarian about a gram-negative antibiotic. We would rather tell you that than sell you the wrong capsule.
Amoxicillin doesn’t treat viral, fungal, or parasitic problems. It can also harm your tank’s good filter bacteria, so watch for that. Check your water. Take extra care with scaleless fish. A fish vet should confirm the cause before you treat.
Fish mox strengths and label rates by tank volume
Fish mox is sold as amoxicillin capsules in two strengths. A 250 mg option and a 500 mg “Forte” option (the strength older keepers knew as Fish Mox Forte or Aqua Mox, and before that Thomas Labs Fish Mox). The quick-reference below scales the manufacturer’s label rate of roughly 250 mg per 10 gallons to common tank sizes. It is the label rate for planning, not a prescription. Your fish veterinarian sets the actual dose, frequency, and duration for your fish.
| Tank volume | Label rate (amoxicillin) | 250 mg capsules | 500 mg capsules |
|---|---|---|---|
| 10 gallons (38 L) | 250 mg | 1 | — |
| 20 gallons (76 L) | 500 mg | 2 | 1 |
| 30 gallons (114 L) | 750 mg | 3 | 1 + one 250 mg |
| 40 gallons (151 L) | 1000 mg | 4 | 2 |
| 55 gallons (208 L) | ~1375 mg | 5–6 | 3 |
Dose by the water volume of your hospital or quarantine tank, not by the number of fish. The bottle label and your aquatic veterinarian always take priority over this quick reference. Fix Mox is the current amoxicillin product that replaced the discontinued Thomas Labs Fish Mox and Aqua Mox lines at the same 250 mg and 500 mg strengths.
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.
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 fish mox
Is fish mox 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 does fish mox treat in fish?
Some bacterial infections, mainly gram-positive or mixed infections a vet has identified. It is a poor match for the gram-negative infections behind dropsy and popeye. A fish vet should confirm the cause and choose the drug.
Is fish mox the same as human amoxicillin?
The active ingredient is the same molecule, but this product is manufactured, labeled, and sold for ornamental aquarium fish only, and isn’t intended or approved for human use.
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.
Why do you tell me when not to use it?
Because we’re a licensed, vet-staffed pharmacy, not a repackager. Selling you the wrong antibiotic wastes your money and harms your fish. Telling you the truth is how we earn your trust.
Is Fix Mox the same as Fish Mox, Fish Mox Forte, or Aqua Mox?
They are the same idea under current labeling. Fish Mox, Fish Mox Forte, and Aqua Mox were earlier amoxicillin products for aquarium use; Fix Mox is the current amoxicillin capsule at the same 250 mg and 500 mg (Forte) strengths. Follow the current bottle label for the amount and duration.
What is the difference between fish mox 250 mg and 500 mg?
It is the strength per capsule. The 250 mg option is the standard strength; the 500 mg option is the “Forte” strength for larger tanks. Match the strength to your hospital-tank volume using the label-rate table above, and let your aquatic veterinarian confirm.
Where can I buy fish mox, do Walmart or Tractor Supply sell it?
General retailers like Walmart, Tractor Supply, and PetSmart don’t reliably carry aquarium amoxicillin. A dedicated vet-staffed pharmacy is the more reliable route, with clear strength labels and fresh stock. You can reserve it here and our pharmacy confirms your order before it ships.
Related guides
Fish dropsy, why amoxicillin is usually the wrong choice, and what to do instead.
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 amoxicillin treats and where it’s a poor match, 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.
