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fish doxycycline 100mg 30 Count - Aquarium Treatment for Gill Disease and Fin Rot
Fish Doxy (Doxycycline) 100mg 60 Count - Fish Antibacterial for Mouth Fungus and Infected Eyes
fish doxycycline 100mg 30 Count - Aquarium Treatment for Gill Disease and Fin Rot
Fish Doxy (Doxycycline) 100mg 60 Count - Fish Antibacterial for Mouth Fungus and Infected Eyes

Fish Doxy (Fix Doxy) Doxycycline 100mg Fish Antibacterial

$44.99
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Doxycycline for Fish and Pet Birds: Fin Rot, Columnaris, Septicemia and Respiratory Infections

Fish Doxy (Fix Doxy) is fish and bird doxycycline in 100 mg tablets for ornamental aquarium fish and non-food pet birds. Aquarists use it for bacterial infections such as fin and tail rot, columnaris, and septicemia in freshwater and saltwater tanks, at one 100 mg tablet per 15 gallons of water, every 24 hours for 5 to 10 days. It is also chosen for racing pigeons and other pet birds during respiratory infections, mycoplasmosis (mycoplasma), or suspected chlamydiosis (also known as parrot fever, psittacosis, or ornithosis).

If you used to buy the discontinued Thomas Labs Fish Doxy, Aqua Doxy, or older Bird Biotic, Fix Doxy is the online replacement. It supplies the same doxycycline strength in bottles of 30 or 60 tablets with fresh expiration dates, and it is a straightforward option when you need doxycycline for birds or a fish doxycycline product to buy online. Hobbyists also shorten the name to fish dox or bird doxy.

Use Fix Doxy when you notice early signs of bacterial stress in your fish or pet birds. Common symptoms differ between species, so check the lists below to identify 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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Fish-Specific Symptoms

  • Clamped or frayed fins (fin and tail rot)
  • Slime disease, mouth fungus / mouth rot
  • Columnaris (cotton wool disease)
  • Red or cloudy patches on the body
  • Bacterial hemorrhagic septicemia
  • Gill disease, labored gill movement
  • Loss of appetite, hiding behavior

Bird-Specific Symptoms

  • Respiratory infections (sneezing, wheezing, nasal discharge)
  • Mycoplasmosis (mycoplasma)
  • Chlamydiosis / ornithosis / psittacosis (parrot fever)
  • Pasteurellosis (common in pigeons)
  • Fluffed-up feathers, lethargy, inactivity
  • Eye infections, persistent loss of appetite
  • Changes in droppings or vocalization

Addressing potential bacterial issues early with doxycycline, together with good water quality and advice from an aquatic or avian professional when available, helps your fish and birds maintain a stable, healthy aquarium or aviary.

Order online and ship directly from our U.S. warehouse. Fix Doxy doxycycline 100 mg tablets are available to buy online with same-day dispatch on orders placed before 1:30 p.m. CT, Monday through Friday.

Fish Doxy vs Fix Doxy: What Changed?

If you used to buy Fish Doxy, Aqua Doxy, or Bird Biotic from Thomas Labs, here is what stayed the same and what is different with Fix Doxy from Aqua Soma Labs.

Same Doxycycline
Fix Doxy delivers the same doxycycline hyclate 100 mg per tablet that was used in the original Fish Doxy and Bird Biotic products.

New Manufacturer
Fix Doxy is made by Aqua Soma Labs, replacing Thomas Labs, which discontinued its Fish Doxy and Bird Biotic lines.

Same Tablet Form
100 mg tablets with the same dosing style (1 tablet per 15 gallons), so switching from Fish Doxy to Fix Doxy requires no changes to your routine.

Updated Packaging & Labeling
New bottle design and labeling under the Fix brand, with the same doxycycline formula and fresh expiration dates.

Benefits of Fix Doxy for Fish & Birds

  • Targets Common Bacterial Problems

    Helps manage common bacterial problems such as fin and tail rot, columnaris, gill disease, septicemia, internal bacterial infections, and avian respiratory infections caused by certain Gram-positive and Gram-negative bacteria in both freshwater and saltwater aquariums.

  • Made in the United States

    Fix Doxy is manufactured by Aqua Soma Labs and ships from a U.S. warehouse with fresh expiration dates, so you receive a recently made product ready for your tank or aviary.

  • One Solution for Fish & Birds

    Fix Doxy is formulated for both ornamental aquarium fish and non-food pet birds, so one doxycycline product covers tanks and aviaries. Use it for individual treatment or a whole flock as appropriate.

  • Fixed 100 mg Tablets

    Each tablet delivers a fixed 100 mg doxycycline amount. These fish doxycycline tablets make it easier to follow the charts and repeat treatments accurately across different tank volumes or bird sizes.

  • Flexible Use in Tanks & Feed

    Tablets are water-soluble and easy to crush, so you can dissolve them in a hospital or quarantine tank, or mix them with food or drinking water as directed. This helps when you need to treat sensitive fish or birds.

  • Available in 30-Count and 60-Count Bottles

    Choose a 30-count bottle for a single treatment or a 60-count bottle for larger tanks, multiple birds, or repeat treatments, so you always have doxycycline on hand when needed.

  • Direct Fish Doxy & Bird Biotic Replacement

    Fix Doxy replaces the discontinued Fish Doxy (Thomas Labs), Aqua Doxy, and Bird Biotic products. It delivers the same doxycycline hyclate 100 mg per tablet that hobbyists and breeders used before those lines were discontinued.

Usage Guidelines & Instructions

Directions for Use:

  1. Prepare a Separate Treatment Area

    For fish, set up a hospital or quarantine tank with clean, dechlorinated water so you can treat without disturbing the main display tank or its biofilter. Any aquarium doxycycline treatment works best in a separate tank, so remove activated carbon, resins and UV sterilizers during dosing, as they can strip doxycycline from the water.

  2. Calculate and Give the Dose

    Fish: Check the dosing instructions on your Fix Doxy bottle. Label directions for 100 mg tablets typically call for 1 tablet (100 mg) per 15 gallons (57 L) of water, repeated every 24 hours for several days. Pre-dissolve the tablet in a small cup of tank water, then add it evenly around the treatment tank.

    Birds: For companion birds, the amount is based on the bird's weight or the volume of treated drinking water. Crush the tablet and mix with soft food or a measured amount of drinking water only as directed on the packaging or by an avian veterinarian, making sure the bird receives the full intended amount.

  3. Monitor Progress and Water Quality

    Watch appetite, breathing, activity level and fin or feather condition every day. If symptoms worsen or no improvement is seen after several days, contact a veterinarian. For fish, perform partial water changes between doses if water quality declines, then re-dose for the new water volume. Continue treatment for the full number of days recommended on the label, usually around 5 to 10 days, unless your vet advises otherwise, and never exceed label directions.

Fix Doxy Amounts by Aquarium Size
Tank volume 100 mg tablets per use
15 gallons (57 L) 1
30 gallons (114 L) 2
45 gallons (170 L) 3
60 gallons (227 L) 4
75 gallons (284 L) 5

These figures follow the label directions of one dissolved tablet per 15 gallons of water. Dose by the water volume of your treatment tank, not by the number of fish, give one dose every 24 hours with a partial water change between doses, and round to the nearest practical tablet. 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 discolored. 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. The label says to discontinue use if no improvement is seen after 5 days, so 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 number of days so the infection does not return. Afterward, run a partial water change and put activated carbon back in to clear any leftover doxycycline.

What You Need for 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 for dissolving each tablet.

Pro Tip: Keep a few extra Fix Doxy tablets on hand so you always have them ready at the first sign of bacterial stress. A quarantine tank with a heater and sponge filter makes treatment faster and protects your main system.

How Fix Doxy Works

Fix Doxy uses doxycycline hyclate 100 mg per tablet to help control certain Gram-positive and Gram-negative bacteria linked with fin and tail rot, mouth rot, columnaris, gill disease, septicemia, and avian respiratory infections. The tablets dissolve readily in aquarium water, and they can also be crushed and mixed with soft food or drinking water, which spreads the dose evenly through a treatment tank or across a flock.

Safety and Tank Notes

When used as directed, Fix Doxy usually causes no problems in ornamental fish and pet birds. As with any doxycycline product, incorrect amounts or prolonged use can increase the risk of side effects.

  • Fish

    Doxycycline based fish treatments may cause temporary stress or hiding behavior, mild water discoloration and reduced appetite during treatment. If fish show severe distress such as rapid gill movement, loss of balance or gasping at the surface, stop treatment and seek aquatic veterinary advice.

  • Birds

    When doxycycline is given in food or drinking water, potential reactions can include decreased appetite, lethargy or changes in droppings if the amount is too high or the bird is sensitive. If your bird appears fluffed up, inactive or stops eating, discontinue use and contact an avian veterinarian.

  • Invertebrates

    Do not use Fix Doxy in tanks that contain shrimp, snails, or other invertebrates, as strong treatments may harm them. Treat fish in a separate hospital tank whenever possible.

  • Safe Use in Your System

    Whenever possible, treat fish in a hospital or quarantine tank, remove activated carbon and UV sterilizers and follow label directions for dose and duration. Do not mix Fix Doxy with other treatments unless advised by a veterinarian.

  • Important Safety Warning

    Fix Doxy is intended for ornamental aquarium fish and non-food pet birds only. It is not for animals raised for food. Store the product in a cool, dry place away from children and pets. Always follow label directions.

Shipping & Returns

Shipping Policy: Orders ship from our U.S. warehouse within 1 business day via USPS or UPS, with rates and delivery times calculated at checkout. For full shipping details, please review our shipping policy.

Refund Policy: If there is an issue with your order, you may be able to return or exchange items within 30 days according to our store guidelines. Before sending anything back, please review our refund policy carefully.

More Fish & Bird Treatments

Fix Zole (Metronidazole) 250/500mg A treatment for Hexamita, hole-in-the-head disease, and other protozoa-related problems in ornamental fish. Available in 60-count bottles. Shop Fix Zole

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

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

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

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

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

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

Fix Flox (Ciprofloxacin) 500mg A treatment for gram-negative bacterial problems, including fin rot, ulcers, columnaris, and septicemia, in ornamental fish and non-food pet birds. Shop Fix Flox

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 doxy?

Fish doxy is a common name for doxycycline sold as an aquarium and aviary treatment. Fix Doxy is the current version: doxycycline hyclate 100 mg tablets for ornamental fish and non-food pet birds. It is used for bacterial problems like fin and tail rot, columnaris, gill disease, and septicemia, not fungi, viruses, or parasites such as ich and flukes.

What is Fix Doxy used for?

Fix Doxy is a doxycycline hyclate 100 mg antibacterial treatment for ornamental aquarium fish and non-food pet birds. It is used when bacterial problems such as fin and tail rot, columnaris, gill disease, septicemia or respiratory infections in birds are suspected and a veterinarian or experienced aquatic or avian keeper recommends a doxycycline product. It does not treat parasitic, viral or fungal conditions.

What is the difference between Fish Doxy and Fix Doxy?

Fish Doxy was a doxycycline 100 mg product made by Thomas Labs, which has been discontinued. Fix Doxy is a replacement made by Aqua Soma Labs using the same doxycycline hyclate 100 mg and the same tablet-based dosing style. The main difference is the manufacturer and packaging; the doxycycline, strength and general usage directions are the same.

Is Fix Doxy a replacement for Bird Biotic?

Yes. Bird Biotic was a doxycycline hyclate 100 mg product from Thomas Labs intended for pigeons, pet birds, and exotic birds. Fix Doxy contains the same doxycycline at the same strength and can be used for non-food pet birds in the same way. Follow the Fix Doxy label directions for avian dosing.

Is Fix Doxy the same as Aqua Doxy?

Aqua Doxy was another doxycycline based fish treatment brand. Fix Doxy from Aqua Soma Labs uses the same doxycycline hyclate 100 mg and serves the same purpose. If you previously used Aqua Doxy for your aquarium or aviary, Fix Doxy is a suitable replacement with the same dosing strength.

Is Fix Doxy available in 500 mg?

Fix Doxy is only available as 100 mg tablets. If a higher total dose is needed, use multiple 100 mg tablets according to label directions or veterinary guidance. For example, a 500 mg total dose would require five 100 mg tablets. Always measure tank volume or bird body weight carefully before increasing the amount, and never exceed the dosing schedule printed on the Fix Doxy label.

What is the fish doxycycline 100mg dosage?

The fish doxycycline 100mg dosage guide is one 100 mg tablet per 15 gallons (57 L) of tank water, dosed every 24 hours for 5 to 10 days, with a partial water change between doses. A 30-gallon hospital tank takes 2 tablets. Discontinue use if there is no improvement after 5 days, and follow the bottle label or your aquatic veterinarian.

Can Fix Doxy be used for pigeons and other pet birds?

Doxycycline has a long history of use in avian care, including for racing pigeons, parrots, finches, canaries, and other companion birds. Fix Doxy delivers the same doxycycline hyclate 100 mg that was available in Bird Biotic products used by pigeon fanciers and bird breeders. The amount and duration must match the bird's species, size, and condition, so follow the Fix Doxy label directions for non-food pet birds or consult an avian veterinarian before treating. Fix Doxy should not be used for chickens, ducks, or other food-producing birds.

Where can I buy doxycycline for fish? Do Walmart or Tractor Supply sell it?

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

Browse Fish & Bird Treatments Collection →
Can fish doxy be used for dogs, cats, or chickens?

No. Fix Doxy is labeled and intended for ornamental aquarium fish and non-food pet birds only. It is not appropriate for dogs, cats, or food-producing animals (including chickens, ducks, turkeys, or other poultry). For dogs and cats, doxycycline should be handled by a veterinarian who can recommend the correct amount and a suitable formulation for the species. Food-producing animals are subject to separate rules and must be treated under veterinary oversight so that withdrawal periods are observed. If your dog, cat, or food-producing animal needs antibacterial treatment, please consult a licensed veterinarian.

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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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