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Fish Ciprofloxacin (Fish Flox) 500mg 30 Count - Advanced Treatment for Fish Columnaris and Ulcers
Fish Flox (Ciprofloxacin) 500mg 60 Count - Ornamental Fish Antibacterial for Gram-Negative Bacteria
Fish Ciprofloxacin (Fish Flox) 500mg 30 Count - Advanced Treatment for Fish Columnaris and Ulcers
Fish Flox (Ciprofloxacin) 500mg 60 Count - Ornamental Fish Antibacterial for Gram-Negative Bacteria

Fish Flox (Fix Flox) Ciprofloxacin 500mg Fish Antibacterial

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Ciprofloxacin for Fish: Fin Rot, Ulcers and Columnaris in Freshwater and Saltwater Tanks

Fish Flox (Fix Flox) from Aqua Soma Labs is an antibacterial treatment for ornamental aquarium fish and non-food pet birds. Each capsule holds 500 mg of ciprofloxacin, which works in the water to help manage suspected bacterial problems such as persistent fin and tail rot, columnaris-type patches, and ulcer-like sores when used as directed. The standard aquarium amount is one 500 mg capsule per 10 gallons (38 L) of water, once every 24 hours for 5 to 10 days.

In the hobby it is still called Fish Flox, Fish Flox Forte, or Aqua Cipro. Fix Flox, from the Aqua Soma Labs Fix range, is the online replacement for the discontinued Thomas Labs Fish Flox and Aqua-Cipro 500 mg. Aquarists who used to buy fish cipro or a fish ciprofloxacin 500 mg capsule will recognize it as the same product under a new label.

Start treatment early, at the first signs of bacterial stress. Those signs differ between fish and birds, so use the lists below to know what to watch for.

Important Notice: This product is intended for aquarium and ornamental fish and pet birds only. It is not for animals used for food.

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This capsule helps with common bacterial problems: persistent fin and tail rot, columnaris-type patches, ulcer-like sores, red sores, hemorrhagic septicemia, swim bladder disease that involves bacteria, and dropsy-like swelling that is often linked to organisms such as Aeromonas, Pseudomonas, Vibrio, or Flavobacterium. Reef keepers also use ciprofloxacin for anemone bacterial infections (deflating or "melting" anemones) in a separate hospital tank.

Fish-Specific Symptoms

  • Fin and tail rot (frayed or rotting fins)
  • Ulcer-like sores or open wounds
  • Red sores or red streaking on the body
  • Dropsy-like swelling
  • Columnaris-type patches
  • Cloudy patches that do not clear with better water quality
  • Lethargy, loss of appetite, or fast decline in activity

Bird Signs (Under Veterinary Guidance)

  • Fluffed-up feathers, lethargy, or inactivity
  • Decreased appetite
  • Loose or changed droppings
  • Labored or difficult breathing
  • Any sudden change a vet links to a bacterial problem

For birds, only use Fix Flox when an avian veterinarian has recommended ciprofloxacin for a specific problem and has set the amount. Catching a bacterial problem early, paired with stable water quality, good aeration, and suitable housing, gives your fish and birds the best chance to recover.

It comes in 30-count and 60-count bottles with fresh expiration dates, so you can buy the amount that fits your situation, whether that is a single hospital tank, several community aquariums, or ciprofloxacin for birds under avian veterinary guidance.

Order before 1:30 p.m. CT, Monday through Friday, and your order ships the same day from our U.S. warehouse via USPS or UPS.

Fish Flox vs Fix Flox: What Changed?

If you previously purchased Thomas Labs Fish Flox, Fish Flox Forte, or Aqua Cipro, here is what changed and what stayed the same:

Same Ciprofloxacin Strength Fix Flox has the same 500 mg of ciprofloxacin per capsule you used in Fish Flox Forte and Aqua Cipro, and the formula works on the same bacteria.

New Manufacturer Fix Flox is made by Aqua Soma Labs, which replaced the discontinued Thomas Labs line and manufactures in the United States.

Same Capsule Form The capsule is the same format as the original Fish Flox, so it opens and dissolves in aquarium water the same way, or you can follow your vet's directions for birds.

Available in 30-Count and 60-Count Bottles Pick the size that fits your setup: a 30-count bottle for a single hospital tank or occasional use, or a 60-count bottle for larger collections and longer treatments.

Benefits of Fix Flox for Fish & Birds

  • Wide Bacterial Coverage

    As a ciprofloxacin treatment, Fix Flox is generally described as helpful against many gram-negative bacteria and some gram-positive ones. Aquarists use ciprofloxacin treatments like Fix Flox for stubborn infections that may involve organisms such as Aeromonas, Pseudomonas, Vibrio, or Flavobacterium.

  • Made in the United States

    Fix Flox is manufactured in the United States by Aqua Soma Labs and ships with fresh expiration dates, so you receive recent stock rather than product that has been sitting on a shelf.

  • Helps Manage Common Aquarium Bacterial Problems

    As an aquarium ciprofloxacin treatment, Fix Flox is often chosen for stubborn fin rot, columnaris-type patches, bacterial gill irritation, ulcer-like sores, red streaking, hemorrhagic septicemia, or dropsy-like swelling tied to a bacterial infection. It is also used for anemone bacterial infections in a separate hospital tank.

  • Consistent 500 mg Capsules

    Each capsule is a fixed 500 mg, which keeps dosing in a quarantine or hospital tank simple to calculate.

  • Easy to Administer

    The capsule holds powder that opens and dissolves easily. Mix it in a small cup of aquarium water first, then spread it evenly around the treatment tank. The same method works for tanks of different sizes.

  • Versatile for Freshwater, Saltwater & Aviary Setups

    Aquarists use Fix Flox in both freshwater and marine hospital tanks. For pet birds, give it only under avian veterinary guidance, when a vet decides it is appropriate for a serious bacterial problem.

  • Ideal for Hospital Tanks and Quarantine

    A separate hospital tank protects your main aquarium's biofilter and keeps healthy tank mates away from the treatment while you treat the fish that need it.

Usage Guidelines & Instructions

Directions for Use: Always follow the directions printed on your bottle. The steps below cover the usual aquarium-water method for ornamental fish.

  1. Set Up a Separate Treatment Area

    Move affected fish to a dedicated hospital tank when you can. A separate tank makes dosing and observation easier and keeps the treatment away from healthy tank mates and your main system's biofilter.

  2. Prepare and Add the Treatment

    Open the capsule and dissolve the powder in a small cup of aquarium water, then spread it evenly around the treatment tank. Use one capsule (500 mg) per 10 gallons (38 L) of water you are treating.

  3. Repeat and Maintain Water Quality

    Repeat the dose every 24 hours. Do a partial water change between doses to keep ammonia and nitrite low, keep the aeration strong, and hold the tank stable. Continue once a day for 5 to 10 days.

  4. Use in Pet Birds (Under Avian Veterinary Guidance)

    Give Fix Flox to pet birds only under the direction of an avian veterinarian. Do not use the aquarium-water directions to work out a bird's amount. Your vet will set the correct amount for the bird's weight, plus the frequency and duration for the species and condition.

  5. Complete the Full Treatment

    Finish the full recommended number of days even if the fish look better, because stopping early can let the bacteria recover. If you see no improvement after 5 days, stop use as directed on the label and ask an aquatic professional for guidance.

Fix Flox Amounts by Aquarium Size
Tank volume Ciprofloxacin per use 500 mg capsules
10 gallons (38 L) 500 mg 1
20 gallons (76 L) 1000 mg 2
30 gallons (114 L) 1500 mg 3
40 gallons (151 L) 2000 mg 4
55 gallons (208 L) about 2750 mg 5 to 6

These figures come from the label guideline of one 500 mg capsule per 10 gallons, about 50 mg per gallon. Dose by the water volume of your treatment tank, not by the number of fish, give one dose every 24 hours for 5 to 10 days, and round to the nearest practical capsule. The bottle label or your aquatic veterinarian takes priority over this quick-reference chart.

What to Expect During Treatment

Days 1 to 2

Fish may hide or eat less, and the water can look slightly cloudy. This is normal early on. Keep dosing on schedule and keep aeration strong.

Days 3 to 5

Look for signs it is working: sores and red patches stop spreading, appetite starts to return, and breathing steadies. If there is no change by day 5, or the fish look worse, stop and ask an aquatic veterinarian.

Days 5 to 10

Even if the fish are improving, finish the full set of treatment days so the infection does not return. Afterward, run a partial water change and put activated carbon back in to clear any leftover treatment.

What You Need for a Treatment

A little setup before the first dose saves trouble later.

  • A separate hospital or quarantine tank, so you are not treating the whole display.
  • A heater and an air stone or sponge filter for steady temperature and strong aeration.
  • An ammonia and nitrite test kit to keep tabs on water quality.
  • A dechlorinator for the water changes between doses.
  • A small net and a clean cup for gentle transfer and measuring the dose.

Pro Tip: Quarantine sick fish away from healthy ones during treatment. A small hospital tank with a heater, an air stone, and no substrate makes dosing and water changes easier. Take out activated carbon and switch off UV sterilizers during treatment, since both can lower the treatment level in the water.

How Fix Flox Works

Each capsule holds 500 mg of ciprofloxacin. In simple terms, it works in the water to slow down or stop the growth of certain bacteria when used as directed for ornamental fish. For pet birds, use it only under avian veterinary guidance.

The rest of the capsule is the shell and standard ingredients that keep the contents stable on the shelf and let them disperse once you dissolve them in aquarium water.

Safety and Tank Notes

When used as directed, this product usually causes no problems in aquarium fish and non-food pet birds. As with any antibacterial treatment, the wrong amount or prolonged use raises the risk of side effects and resistance.

  • Fish

    Some fish may hide, eat less, act mildly lethargic, or the water may cloud temporarily during treatment. If a fish shows severe distress, such as rapid gill movement, loss of balance, gasping at the surface, or lying on the bottom, stop treatment, improve aeration, and get aquatic veterinary advice.

  • Birds

    Give Fix Flox to birds only under avian veterinary guidance. A bird may eat less, act lethargic, or pass loose or changed droppings, especially if it is sensitive or the amount is off. If your bird looks fluffed up, inactive, or stops eating, stop use and contact an avian veterinarian.

  • Invertebrates

    Do not use Fix Flox in display tanks with shrimp, snails, or other invertebrates, since these treatments can harm them or upset the tank ecosystem. Whenever you can, move affected fish to a separate hospital tank.

  • Safe use in your system

    Treat fish in a hospital or quarantine tank whenever possible. Remove activated carbon and turn off UV sterilizers during treatment, and watch ammonia, nitrite, and temperature closely. Do not mix this product with other treatments unless a veterinarian tells you to.

  • Important safety warning

    This product is for ornamental aquarium fish and non-food pet birds only. It is not for animals raised for food. Store capsules in a cool, dry place away from direct sunlight, and keep them away from children and pets. Always follow the directions on the label.

Shipping & Returns

Shipping Policy: Orders ship from our U.S. warehouse within 1 business day via USPS or UPS, and orders placed before 1:30 p.m. CT (Monday through Friday) ship the same day. For full details, see our shipping policy.

Refund Policy: If something is wrong with your order, you may be able to return or exchange items within 30 days under our store guidelines. Before you send anything back, please read our refund policy carefully.

More Fish & Bird Treatments

Fix Mox (Amoxicillin) 250/500mg A treatment for fin rot, dropsy, ulcers and other bacterial infections in ornamental fish. Available in 30-count and 100-count capsules. Shop Fix Mox Amoxicillin

Fix Zole (Metronidazole) 250/500mg Targets anaerobic bacteria and protozoa including Hexamita and hole-in-the-head disease in ornamental fish. Available in 60-count bottles. Shop Fix Zole Metronidazole

Fix Doxy (Doxycycline) 100mg A treatment for columnaris, respiratory infections and Mycoplasma in fish and non-food pet birds. Available in 30-count and 60-count tablets. Shop Fix Doxy Doxycycline

Fix Zithro (Azithromycin) 250mg A treatment for fin rot, columnaris, gill disease and avian respiratory concerns. Available in 12-count and 30-count tablets. Shop Fix Zithro Azithromycin

Fix Cin (Clindamycin) 150mg A treatment commonly used for gram-positive bacterial infections including skin and soft tissue concerns in ornamental fish. Shop Fix Cin Clindamycin

Fix Sulfa (SMZ/TMP) 960mg A treatment offering coverage against a range of bacterial infections in ornamental fish. Shop Fix Sulfa SMZ/TMP

Fix Pen (Penicillin) 500mg A treatment for gram-positive bacterial infections in ornamental fish and non-food pet birds. Shop Fix Pen Penicillin

Fix Flex (Cephalexin) 250/500mg A treatment for fin rot, ulcers and bacterial skin infections in ornamental fish and non-food pet birds. Shop Fix Flex Cephalexin

Browse all treatments Explore our complete Fish & Bird Antibacterials Collection for more Fix line products and related treatments.

Guides and treatment tips Visit the Fish & Bird Treatments Blog for practical usage guides, water-care advice and treatment tips.

Frequently Asked Questions

What is fish flox?

Fish flox is a common name for ciprofloxacin sold as an aquarium treatment. Fix Flox is the current version: ciprofloxacin at 500 mg per capsule for ornamental fish and non-food pet birds. Aquarists use it for stubborn bacterial problems such as fin and tail rot, ulcer-like sores, and columnaris-type patches in freshwater and saltwater tanks, not for ich, flukes, or fungus.

What is Fix Flox (Fish Flox) used for in fish and birds?

Fix Flox (ciprofloxacin 500 mg) is an antibacterial treatment that aquarists use for bacterial problems such as persistent fin rot, columnaris-type patches, ulcer-like sores, red sores, hemorrhagic septicemia, and swim bladder disease in ornamental fish. For non-food pet birds, it may be used under avian veterinary guidance for serious bacterial concerns.

What is the difference between Fish Flox and Fix Flox?

Fish Flox was the brand name Thomas Labs used for its ciprofloxacin capsules. After Thomas Labs discontinued the product, Aqua Soma Labs introduced Fix Flox as a direct replacement. It has the same 500 mg of ciprofloxacin per capsule, the same capsule format, and the same ornamental-fish and pet-bird uses.

Is Fix Flox the same as Fish Flox Forte or Aqua Cipro?

Yes. Fish Flox Forte was the name for the 500 mg ciprofloxacin capsule, and Aqua Cipro (Aqua-Cipro 500 mg) was another brand of the same ciprofloxacin. Fix Flox from Aqua Soma Labs is the current direct replacement, with the same 500 mg ciprofloxacin per capsule in 30-count and 60-count bottles. The brand names and packaging changed; the capsule and its intended fish and bird use stayed the same.

What is inside Fix Flox (Fish Flox)?

Fix Flox contains ciprofloxacin at 500 mg per capsule. It is the same ciprofloxacin that was in Thomas Labs Fish Flox and Fish Flox Forte. The rest of the capsule is the shell and standard ingredients that keep the contents stable and let them dissolve in aquarium water.

Is fish cipro the same as Fix Flox?

"Fish cipro" is a common nickname for ciprofloxacin sold as an aquarium treatment. Fix Flox is the current version: ciprofloxacin at 500 mg per capsule for ornamental fish and non-food pet birds. It is the same ciprofloxacin for the same bacterial problems, just under a current label with fresh stock, and it replaces the older Thomas Labs fish ciprofloxacin and Aqua Cipro products.

What is the fish ciprofloxacin dosage?

The standard fish ciprofloxacin dosage is one 500 mg capsule per 10 gallons (38 L) of tank water, about 50 mg per gallon, once every 24 hours for 5 to 10 days, with a partial water change between doses. Dose by the water volume of your treatment tank, not by the number of fish. If there is no improvement after 5 days, stop and ask an aquatic veterinarian. Birds are different: an avian veterinarian sets the amount by body weight, so never work a bird's amount out from the aquarium chart.

What bacteria does ciprofloxacin target in fish?

Ciprofloxacin is generally described as helpful against many gram-negative bacteria, including organisms such as Aeromonas, Pseudomonas, Vibrio, and Flavobacterium, and against some gram-positive bacteria. It works inside the bacteria to stop them from copying their DNA, which slows or stops their growth.

Where can I buy ciprofloxacin for fish? Do Walmart or PetSmart sell it?

You can order Fix Flox, the current fish ciprofloxacin, directly from Fine Pet Health in 30-count and 60-count bottles of 500 mg capsules. General retailers such as Walmart, PetSmart, Petco, and Tractor Supply do not carry the Aqua Soma Labs line, so a dedicated online supplier is the reliable route. Orders ship from our U.S. warehouse via USPS or UPS, with same-day dispatch on orders placed before 1:30 p.m. CT, Monday through Friday.

Browse Fish & Bird Treatments Collection →
Can Fix Flox treat fungal, viral, or parasitic infections?

No. This product works on certain bacterial infections only. It does nothing for fungi, viruses, or parasites such as ich, flukes, or worms. For a fungal, parasitic, or viral problem, work with an aquatic or avian veterinarian to pick the right treatment instead.

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Who is responsible for this page: the Fine PetHealth Editorial Team, part of Fine PetHealth Group LLC, a US-based pet supplies retailer.

How this page was created: prepared with AI assistance, verified against the current product label, and reviewed by a person before publishing. How we verify product information.

Educational use only: this page is not a substitute for advice from your veterinarian. If something does not match the product you received, let us know.

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