Fish Zithro (Azithromycin 500mg) tablets deliver advanced macrolide-class antibiotic treatment for ornamental and aquarium fish battling bacterial infections that standard penicillin or cephalosporin antibiotics may not fully address. Each tablet contains 500mg of Azithromycin — a broad-spectrum macrolide antibiotic that works by inhibiting bacterial protein synthesis, effectively stopping harmful bacteria from growing and reproducing at the cellular level.
What sets Fish Zithro apart from other fish antibiotics is its long-lasting action. Azithromycin's extended half-life means therapeutic levels remain active in your tank longer than many other antibiotics — reducing the frequency of dosing and minimizing stress on your fish during the treatment period. This makes Fish Zithro one of the most practical and fish-friendly antibiotic options available for ornamental aquarium care.
Fish Zithro is particularly effective against columnaris (Flavobacterium columnare) — one of the most aggressive and fast-spreading bacterial diseases in aquarium fish — as well as gill disease, fin rot, ulcers, mouth rot, popeye, swim bladder disease, and bacterial septicemia. Tablets dissolve easily in tank water or can be mixed directly into fish food for targeted internal treatment. Available at CalVetSupply without a vet prescription for ornamental and aquarium fish use only.
ACTIVE INGREDIENT
Azithromycin 500mg per tablet
WHAT DOES FISH ZITHRO TREAT?
Fish Zithro (Azithromycin 500mg) is effective against a wide range of bacterial conditions in ornamental freshwater and saltwater fish including:
- Columnaris (Flavobacterium columnare / Cotton Wool Disease)
- Bacterial gill disease
- Fin rot & tail rot
- Mouth rot
- Skin ulcers & open lesions
- Popeye (exophthalmia)
- Swim bladder disease (bacterial origin)
- Bacterial septicemia
- Aeromonas & Vibrio infections
- Mycobacterium-related conditions
- Internal & external bacterial infections
WHY FISH ZITHRO WORKS DIFFERENTLY
Most fish antibiotics like Fish Mox (Amoxicillin) and Fish Flex (Cephalexin) work by destroying bacterial cell walls. Fish Zithro takes a completely different approach — Azithromycin targets and shuts down bacterial protein synthesis, blocking the 50S ribosomal subunit that bacteria need to produce proteins essential for survival and reproduction.
This distinct mechanism makes Fish Zithro effective against bacterial strains that have developed resistance to cell-wall-targeting antibiotics — and particularly powerful against the gram-negative and intracellular bacteria responsible for columnaris and gill disease in aquarium fish.
TWO WAYS TO USE FISH ZITHRO
Method 1 — Water Treatment (External & General Infections)
- Remove activated carbon from filter before starting treatment
- Dissolve one tablet per 10 gallons of aquarium water
- Treat daily for 5–7 days
- Perform partial water changes as needed to maintain water quality during treatment
- Quarantine infected fish in a hospital tank when possible to protect your main tank
Method 2 — Food Treatment (Internal Infections)
- Crush tablet and mix thoroughly into fish food
- Feed treated food directly to affected fish daily
- Continue for 5–7 days
- Use this method when internal bacterial infection such as swim bladder disease or septicemia is suspected
WHEN TO USE FISH ZITHRO
Fish Zithro is the right choice when your ornamental fish shows:
- White or grey cottony patches on body or fins (columnaris)
- Rapid or labored gill movement suggesting gill disease
- Frayed or eroding fins alongside skin discoloration
- Mouth deterioration or rot
- Bulging or cloudy eyes (popeye)
- Bloating or abnormal swimming linked to swim bladder bacterial infection
- Bacterial infection that has not responded to Fish Mox or Fish Flex treatment
Fish Zithro treats bacterial infections only — it is not effective against fungal or parasitic conditions.
FISH ZITHRO VS OTHER FISH ANTIBIOTICS
| Fish Zithro (Azithromycin) | Fish Mox (Amoxicillin) | Fish Flex (Cephalexin) |
|---|
| Class | Macrolide | Penicillin | Cephalosporin |
| Mechanism | Protein synthesis inhibition | Cell wall disruption | Cell wall disruption |
| Best For | Columnaris, gill disease, resistant strains | Dropsy, broad infections | Skin, wounds, soft tissue |
| Half-Life | Long-lasting | Standard | Standard |
| Admin | Water or food | Water | Water or food |
PRECAUTIONS & SAFETY
- For ornamental aquarium fish use only
- Not for use with fish intended for human consumption
- Always remove activated carbon before water treatment
- Quarantine infected fish in a hospital tank when possible
- Do not combine with other medications without consulting an aquatic veterinarian
- Complete the full 5–7 day course to prevent antibiotic resistance
- Monitor water parameters closely throughout treatment
- Keep out of reach of children and pets
- Store in a cool dry place away from direct sunlight
FAQ
Q: What is Fish Zithro used for?
A: Fish Zithro (Azithromycin 500mg) treats columnaris, bacterial gill disease, fin rot, mouth rot, popeye, swim bladder disease, bacterial septicemia, and Aeromonas and Vibrio infections in ornamental aquarium fish.
Q: Why choose Fish Zithro over Fish Mox or Fish Flex?
A: Fish Zithro works through protein synthesis inhibition — a completely different mechanism from Fish Mox and Fish Flex which target bacterial cell walls. This makes Fish Zithro effective against resistant bacterial strains and gram-negative pathogens like columnaris that don't respond well to penicillin or cephalosporin treatment.
Q: Does Fish Zithro have a long-lasting effect?
A: Yes. Azithromycin has an extended half-life compared to most other fish antibiotics — maintaining therapeutic levels in your tank longer and reducing the need for frequent dosing during treatment.
Q: Can Fish Zithro treat internal infections?
A: Yes. Crush the tablet and mix into fish food for targeted internal delivery — particularly effective for swim bladder disease and septicemia with a bacterial origin.
Q: Do I need a prescription to buy Fish Zithro?
A: No. Fish Zithro is available at CalVetSupply without a vet prescription for ornamental aquarium fish use only.
Q: Can Fish Zithro be used in saltwater tanks?
A: Yes. Fish Zithro is effective in both freshwater and saltwater aquariums. Always follow label dosage directions.
Q: How long does Fish Zithro treatment take?
A: Treat daily for 5–7 days. Always complete the full course even if symptoms improve early to prevent antibiotic resistance.
Q: Does Fish Zithro affect beneficial bacteria?
A: Fish Zithro has a comparatively lower impact on beneficial aquarium bacteria than many broad-spectrum antibiotics. Treating in a hospital tank further minimizes any disruption to your main tank's biological filtration.
Q: What if my fish shows no improvement after treatment?
A: Discontinue use and consult an aquatic veterinarian. Persistent symptoms may require a different antibiotic such as Fish Flox (Ciprofloxacin) or a more specific diagnosis.
