Broad-spectrum tetracycline-class antibiotic — effective for both freshwater and saltwater ornamental fish, available in capsule and tablet form.

Capsule or Tablet? Both forms contain identical USP-grade Doxycycline Hyclate 100mg and the same dosing instructions. Capsules dissolve slightly faster in water. Tablets are easier to split for precise dosing in smaller tanks. Choose based on your preference — the treatment outcome is the same.

Why choose Doxycycline? Doxycycline belongs to the tetracycline antibiotic class and is one of the most versatile aquarium antibiotics available. Unlike standard tetracycline, doxycycline remains stable and effective in both freshwater and saltwater tanks — it does not bind to calcium ions and lose potency in hard or salt water. It is a top choice for treating tail rot, gill infections, swim bladder disease, and slow-healing wounds, and is widely considered one of the best all-around antibiotics for ornamental fish.

About This Product

Doxycycline Hyclate is a broad-spectrum tetracycline-class antibiotic effective against a wide range of gram-negative and gram-positive bacterial microorganisms. It works by inhibiting bacterial protein synthesis — preventing bacteria from reproducing and allowing the fish's immune system to clear the infection naturally.

Each capsule or tablet contains USP-grade Doxycycline Hyclate 100mg, available in a 100-count. A key advantage of doxycycline over standard tetracycline is its stability in both freshwater and saltwater environments — it does not bind to the calcium and magnesium ions found in hard water and marine tanks, making it fully effective regardless of water chemistry. It is one of the most widely used and recommended antibiotics in ornamental fishkeeping.

Also commonly searched as: fish doxy, doxycycline for fish, aqua doxy equivalent, fish doxycycline 100mg, tetracycline fish antibiotic, aquarium doxycycline.

Commonly Treats

• Tail rot & fin rot
• Gill disease & gill infections
• Swim bladder disease (bacterial)
• Slow-healing wounds & ulcers
• Bacterial hemorrhagic septicemia
• Dropsy
• Columnaris (mouth rot)
• Internal & systemic bacterial infections

Directions for Use

1. Determine your dose: Use one 100mg capsule or tablet per 10 gallons of aquarium water. Dosing is identical for both forms.
2. Dissolve the capsule or tablet in a small amount of aquarium water before adding to the tank. Stir until fully dissolved.
3. Add directly to your aquarium, pond, or hospital/quarantine tank.
4. Repeat every 24 hours for 5–10 days. Do not exceed 10 days of continuous treatment.
   
5. Perform a 25% water change each day before re-dosing to maintain water quality and reduce antibiotic buildup.

Product Specifications

• For ornamental fish use only. Not intended for use in fish raised for human consumption.
• Not for human consumption. Do not ingest. This product is sold for aquarium fish treatment only.
• Keep out of reach of children. Store in a cool, dry place away from children and pets.
• Do not exceed 10 days of continuous treatment. Overuse may contribute to antibiotic resistance in your aquarium ecosystem.
• Remove activated carbon from your filter before treatment — carbon will absorb the medication and render treatment ineffective.
• Avoid direct light exposure during treatment. Doxycycline degrades rapidly under UV and direct sunlight — dim tank lighting or cover the tank during the treatment period for best results.

Label & Usage Disclaimer: Please read and follow all label directions before use. Product descriptions and usage instructions shown here are taken directly from the manufacturer’s product label and information provided by Montana Aquarium Supply. These statements do not represent the views or recommendations of Pittsboro Pet Supply. Made in the USA. Distributed by Montana Aquarium Supply – Billings, MT.