Fix Doxy (Fish Doxy) Doxycycline Tablets - 100 mg

Fix Doxy (Fish Doxy) Doxycycline 100mg is a broad-spectrum doxycycline tablet for ornamental aquarium fish and non-food pet birds, manufactured by Aqua Soma Labs. Hobbyists know it as a reliable online replacement for discontinued Thomas Labs Fish Doxy, Aqua Doxy, and older Bird Biotic products.

As an over-the-counter (OTC) part of the Aqua Soma Labs Fix range of aquarium fish antibiotics, this fish and bird antibiotic helps manage common problems such as fin and tail rot, columnaris (often seen as cotton wool disease), bacterial hemorrhagic septicemia, and other internal bacterial infections caused by Gram-positive and Gram-negative bacteria in freshwater and saltwater aquariums. It also reliably supports racing pigeons and other pet birds during respiratory infections, mycoplasmosis (mycoplasma), or suspected chlamydiosis (also known as parrot fever, psittacosis, or ornithosis).

Doxycycline is a broad-spectrum tetracycline antibiotic that works by inhibiting bacterial protein synthesis, limiting the growth of susceptible bacteria in the gills, skin and respiratory tract.

Fix Doxy from Aqua Soma Labs supplies 100 mg doxycycline per tablet and comes in bottles of 30 or 60 tablets with fresh expiration dates, giving hobbyists a reliable option when they need doxycycline for birds or a trusted fish doxycycline product to buy online.

Use Fix Doxy when you notice signs of bacterial stress such as clamped or frayed fins, slime disease, mouth fungus / mouth rot, red or cloudy patches on the body, labored breathing, sneezing and wheezing, nasal discharge or a persistent loss of appetite. 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.

Important Notice: This product is intended for aquarium and ornamental fish and pet birds only. It is not for human consumption or for animals used for food. We do not sell or recommend this product for human use.

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 Active Ingredient
Fix Doxy delivers the same doxycycline hyclate 100 mg per tablet, the same broad-spectrum tetracycline class 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, but the same pharmaceutical-grade quality and fresh expiration dates.

Benefits of Fix Doxy for Fish & Birds

Broad-Spectrum Doxycycline

Helps manage common bacterial problems such as fin and tail rot, columnaris, gill disease, septicemia, internal bacterial infections, and avian respiratory infections caused by susceptible Gram-positive and Gram-negative bacteria in both freshwater and saltwater aquariums.
No Veterinary Prescription Required

Fix Doxy 100 mg is sold as an over-the-counter (OTC) fish and bird antibiotic, so you can order it online without a veterinary prescription in most regions. If you are unsure about local regulations, check with a veterinarian or your local authority.
One Solution for Fish & Birds

Formulated for ornamental aquarium fish and non-food pet birds, so you can rely on a single doxycycline product for both tanks and aviaries, including individual dosing or whole flock treatment when appropriate.
Tablet Form for Consistent Dosing

Each tablet delivers a fixed 100 mg doxycycline dose, making it easier to follow dosing charts and repeat courses accurately across different tank volumes or bird sizes.
Flexible Use in Tanks & Feed

Tablets are water-soluble and easy to crush, meaning they can be dissolved for use in hospital or quarantine tanks, or mixed with food or drinking water as directed, giving you options when dosing sensitive fish or birds.
Available in 30-Count and 60-Count Bottles

Choose a 30-count bottle for a single treatment course or a 60-count bottle for larger tanks, multiple birds, or repeat treatments, so you always have doxycycline on hand when needed.
Trusted Fish Doxy & Bird Biotic Replacement

Fix Doxy is a direct replacement for discontinued Fish Doxy (Thomas Labs), Aqua Doxy, and Bird Biotic products, delivering the same doxycycline hyclate 100 mg per tablet that hobbyists and breeders have relied on for years.

Dosage Guidelines & Instructions

Directions for Use:

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. Remove activated carbon, resins and UV sterilizers during treatment, as they can strip doxycycline from the water.
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, dosing is based on body weight or medicated drinking-water volume. 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 dose.
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 course recommended on the label, usually around 5-10 days, unless your vet advises otherwise, and never exceed label directions.

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 This Medication Works

Active Ingredient: Doxycycline Hyclate 100 mg per Tablet

Doxycycline hyclate is a broad-spectrum tetracycline antibiotic that interferes with bacterial protein synthesis. It helps control susceptible Gram-positive and Gram-negative bacteria linked with fin and tail rot, mouth rot, columnaris, gill disease, septicemia and avian respiratory infections.
Water- and Feed-Friendly Tablet Base

Tablets are formulated to disperse readily in aquarium water or to be crushed and mixed with soft food or drinking water for ornamental aquarium fish and non-food pet birds, helping the dose spread evenly through the treatment tank or flock.

Side Effects & Safety Tips

When used as directed, Fix Doxy is generally well tolerated in ornamental fish and pet birds. As with any doxycycline product, incorrect dosing or prolonged use can increase the risk of side effects.

Fish

Doxycycline based fish antibiotics 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 dose 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 antibiotics 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 antibiotics 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 human use and not for animals raised for food. Using fish antibiotics in people instead of prescribed medicine can lead to treatment failure, serious side effects and antibiotic resistance. Store the product in a cool, dry place away from children. 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.

Frequently Asked Questions

What is Fix Doxy used for?

Fix Doxy is a doxycycline hyclate 100 mg antibiotic 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-class 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 active ingredient (doxycycline hyclate 100 mg) and the same tablet-based dosing style. The main difference is the manufacturer and packaging; the active ingredient, strength and general usage directions are the same.

Is Fix Doxy the same as older Fish Doxy or Bird Biotic tablets?

Fix Doxy uses the same doxycycline hyclate 100 mg strength and similar dosing style as many hobbyists remember from Fish Doxy, Fishdox and Bird Biotic-type products. However, it is its own branded formula from Aqua Soma Labs, and you should always follow the directions printed on the Fix Doxy label.

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 active ingredient 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 antibiotic brand. Fix Doxy from Aqua Soma Labs uses the same active ingredient (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.

Do I need a veterinary prescription to buy Fix Doxy?

Many hobbyists search online for doxycycline for fish without vet prescription. Fix Doxy 100 mg is sold and labeled as an over-the-counter (OTC) aquarium fish and bird antibiotic for ornamental fish and non-food pet birds, and in most regions it is available without a veterinary prescription. However, regulations can change, and serious or recurring infections should always be checked by an aquatic or avian veterinarian, who can confirm whether doxycycline is appropriate and how to use it safely.

Where can I buy doxycycline for fish online?

You can buy Fix Doxy doxycycline 100 mg tablets directly from this page at Fine Pet Health. Orders ship from our U.S. warehouse with same-day dispatch on orders placed before 1:30 p.m. CT, Monday through Friday. Select your preferred bottle size (30-count or 60-count) above and proceed to checkout.

How do I know if my fish or bird might need an antibiotic like Fix Doxy?

Signs of possible bacterial issues can include frayed or reddened fins, open sores, body patches, labored breathing, nasal discharge, fluffed-up feathers, or a sudden drop in appetite. These signs are not specific to one disease, so a veterinarian or experienced aquatic or avian professional should help confirm whether a doxycycline fish and bird antibiotic is appropriate.

How long should I treat with Fix Doxy 100 mg?

Most label directions for doxycycline 100 mg tablets call for a course of about 5-10 days, with doses given every 24 hours. Do not stop early just because symptoms look better, and never extend the course or change the dose beyond what the label or your veterinarian advises.

What size aquarium can one Fix Doxy tablet treat?

Label directions typically call for 1 tablet (100 mg) per 15 gallons (57 L) of water. For a 30-gallon hospital tank you would use 2 tablets per dose. Always measure your treatment tank volume carefully and follow the directions on the Fix Doxy label.

Does Fix Doxy work in saltwater aquariums?

Yes. Fix Doxy is effective against susceptible Gram-positive and Gram-negative bacteria in both freshwater and saltwater aquariums. The same dosing directions apply. As always, treat in a hospital or quarantine tank whenever possible to protect your main system's biofilter and invertebrates.

Can I use Fix Doxy in my main display or community tank?

It is usually better to treat in a hospital or quarantine tank. Like other broad-spectrum aquarium antibiotics, Fix Doxy can affect beneficial biofilter bacteria in a community tank. Treating separately helps protect your main system and makes it easier to monitor sick fish.

Will Fix Doxy harm my aquarium's biofilter?

Any strong antibacterial treatment can impact nitrifying bacteria if used in the main tank. Using a separate treatment tank, monitoring ammonia and nitrite, and performing partial water changes as directed helps reduce the risk to your biofilter.

Can Fix Doxy be used for racing pigeons?

Doxycycline has a long history of use in avian medicine, including for racing pigeons. Fix Doxy delivers the same doxycycline hyclate 100 mg that was available in Bird Biotic products used by pigeon fanciers. Dose and duration must match the bird's species and weight, so follow the Fix Doxy label or consult an avian veterinarian before treating.

Can Fix Doxy be used for multiple bird species?

Doxycycline is commonly used in avian medicine, but dose and duration must match the bird's species, size and condition. Use Fix Doxy for birds only under guidance from an avian veterinarian or according to clear directions from the product label for non-food pet birds.

Can I combine Fix Doxy with other fish medications?

Do not mix Fix Doxy with other antibiotics or medications unless specifically advised by a veterinarian. Combining treatments can reduce effectiveness, cause harmful interactions, or increase stress on fish. If a second medication is needed, finish the doxycycline course first, perform a water change with activated carbon, and then begin the next treatment.

What should I do if my fish or bird is not improving on Fix Doxy?

Stop treatment and contact a veterinarian. Lack of improvement can mean the problem is not bacterial, the bacteria are not susceptible to doxycycline, or the dose or treatment duration is not appropriate. Continuing an ineffective antibiotic can delay proper care.

How should I store Fix Doxy tablets?

Store Fix Doxy in a cool, dry place away from direct sunlight and moisture, with the bottle tightly closed. Keep out of reach of children and pets. Check the expiration date on the packaging and do not use tablets past that date.

How should I dispose of water or filter media that contained Fix Doxy?

After treatment, avoid dumping all medicated water at once into drains that may lead directly to natural ponds, streams or outdoor soil. Instead, carry out several partial water changes and dilute the used aquarium water with plenty of fresh tap water before disposal, following any local guidelines for aquarium water. Used filter media, carbon and disposable decorations that have been exposed to antibiotics should be sealed in a bag and placed in household trash rather than rinsed outdoors, to help protect nearby aquatic ecosystems.

Is Fix Doxy the same as the doxycycline humans take?

No. Even though Fix Doxy uses a doxycycline-class ingredient, it is manufactured, labeled and quality-controlled for fish and birds only. Human medicines must come from a healthcare professional and a licensed pharmacy. Never use Fix Doxy or any fish antibiotic for human treatment or for animals raised for food.

More Fish & Bird Antibiotics

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

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

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

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

Fix Sulfa (SMZ/TMP) 960mg A sulfonamide combination fish antibiotic offering broad-spectrum coverage against a range of bacterial infections in ornamental fish. Shop Fix Sulfa

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

Fix Flex (Cephalexin) 250/500mg A first-generation cephalosporin fish and bird antibiotic for fin rot, ulcers and bacterial skin infections in ornamental fish. Shop Fix Flex

Fix Flox (Ciprofloxacin) 500mg A fluoroquinolone fish and bird antibiotic for gram-negative bacterial infections including fin rot, ulcers, columnaris and septicemia in ornamental fish. Shop Fix Flox

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

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

Fix Doxy (Fish Doxy) Doxycycline Tablets - 100 mg

Fish Doxy vs Fix Doxy: What Changed?

Benefits of Fix Doxy for Fish & Birds

Broad-Spectrum Doxycycline

No Veterinary Prescription Required

One Solution for Fish & Birds

Tablet Form for Consistent Dosing

Flexible Use in Tanks & Feed

Available in 30-Count and 60-Count Bottles

Trusted Fish Doxy & Bird Biotic Replacement

Dosage Guidelines & Instructions

Prepare a Separate Treatment Area

Calculate and Give the Dose

Monitor Progress and Water Quality

How This Medication Works

Active Ingredient: Doxycycline Hyclate 100 mg per Tablet

Water- and Feed-Friendly Tablet Base

Side Effects & Safety Tips

Fish

Birds

Invertebrates

Safe Use in Your System

Important Safety Warning

Shipping & Returns

Frequently Asked Questions

More Fish & Bird Antibiotics

Home page