Fix Flex (Fish Flex) Cephalexin Capsules - Fish & Bird Antibiotic 250 mg / 500 mg
Fix Flex (often called Fish Flex in the hobby community) is a convenient cephalexin fish antibiotic in capsule form for ornamental aquarium fish and non-food pet birds. This fish and bird antibiotic helps manage common bacterial issues such as fin and tail rot, skin ulcers, red patches and mild body swelling in freshwater and saltwater aquariums. The capsules can be opened so the powder dissolves quickly and the dose spreads evenly through the water or a separate hospital tank.
Cephalexin is a first-generation cephalosporin antibiotic that works by disrupting bacterial cell wall formation, making it especially active against susceptible Gram positive bacteria and some Gram negative species.
Fix Flex from Aqua Soma Labs is available in 250 mg and 500 mg strengths and in bottles of 30 or 100 capsules, so you can choose the right option for your aquarium volume or bird flock size.
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.
Use Fix Flex when you notice frayed or ragged fins, red or pale fin edges, open sores, localized swelling or a persistent loss of appetite. Treating suspected bacterial infections early with cephalexin, together with good water quality and advice from an aquatic or avian professional when available, helps your fish and birds recover faster and supports a stable, healthy aquarium or aviary.
Looking for a Reliable Cephalexin for Fish & Birds?
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Cephalexin capsules made for aquarium fish and pet birds
Fix Flex (also known as Fish Flex) delivers cephalexin fish antibiotic capsules formulated for ornamental aquarium fish and non-food pet birds. The powder from each capsule disperses easily in freshwater and saltwater tanks or separate hospital setups.
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Two strengths for flexible dosing: 250 mg and 500 mg
Use 250 mg cephalexin capsules for smaller aquariums, hospital tanks or lightly stocked systems, and 500 mg capsules for larger volumes or when higher total doses are needed, always following the label directions.
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Support for ornamental fish and non-food pet birds
Designed first as a cephalexin fish antibiotic for common bacterial issues such as fin and tail rot, skin ulcers and red sores, and used only under avian veterinary guidance where cephalexin is appropriate for pet birds.
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30- and 100-count bottles from Aqua Soma Labs
Choose the bottle size that fits your setup: enough capsules for a quarantine or hospital tank, multiple display tanks or a small bird flock, without stocking more than you need. All bottles come from Aqua Soma Labs, the maker of the Fix line of fish antibiotics.
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Easy to keep on hand for problem days
Keeping Fix Flex cephalexin capsules in your fish room or bird room means you can respond quickly when problems first appear, while still following local regulations and working with an aquatic or avian professional whenever possible.
How To Use Fix Flex Cephalexin Capsules (250 mg / 500 mg)
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Confirm that Fix Flex is appropriate
Use Fix Flex cephalexin capsules only for ornamental aquarium fish and non-food pet birds when a bacterial problem is suspected. If you are unsure, or before using it for birds, consult an aquatic or avian veterinarian.
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Follow dosage directions on the label
Fix Flex cephalexin fish antibiotic capsules are available in 250 mg and 500 mg strengths. Select the strength that matches your aquarium volume or your professional’s advice, and follow the product label for the number of capsules and how often to dose. Do not increase the dose or shorten the intervals on your own.
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Choose a treatment method
For fish, capsule contents are typically dissolved in a small amount of aquarium water and then added to the main tank or a separate hospital tank as directed. In some protocols, the powder may be carefully mixed with food for more targeted feeding, following label directions or guidance from an aquatic professional. For non-food pet birds, only use Fix Flex under avian veterinary guidance and follow their exact instructions for dose, route and duration.
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Complete the full course and monitor closely
Use Fix Flex for the full course recommended on the label or by your veterinarian, even if your fish or birds start to look better sooner. Check water quality, appetite, activity and appearance each day. If signs worsen or do not improve, stop treatment and seek professional advice instead of extending, repeating or changing the course on your own.
What Are the Ingredients in Fix Flex (Fish Flex) Cephalexin Capsules?
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Active ingredient: Cephalexin Monohydrate
A trusted, broad-spectrum cephalosporin antibiotic supplied in 250 mg and 500 mg capsule strengths for use in ornamental aquarium fish and non-food pet birds.
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Capsule base:
Hard gelatin capsule with standard pharmaceutical excipients selected to protect the cephalexin powder, support shelf life, and help the contents disperse evenly when used as directed.
Side Effects and Safe Use of Fix Flex (Fish Flex) Cephalexin Capsules
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Possible effects in the aquarium:
Like other antibiotics, cephalexin can also affect beneficial filter bacteria if it is overused or dosed incorrectly. This may lead to temporary changes in the nitrogen cycle and spikes in ammonia or nitrite, so always monitor water parameters closely during treatment and perform partial water changes as needed.
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Possible reactions in fish and birds:
Any medication can cause sensitivity reactions in some animals. Watch your ornamental aquarium fish and non food pet birds for changes such as reduced appetite, unusual hiding, labored breathing or swelling. If signs worsen or new problems appear, stop using Fix Flex and contact an aquatic or avian professional.
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Responsible use and storage:
Use Fix Flex cephalexin capsules only when a bacterial problem is suspected and follow the dosage and duration on the product label or from your veterinarian to help limit antibiotic resistance. Keep capsules in their original container in a cool, dry place, out of reach of children and animals, and never use fish antibiotics for yourself or for other mammals.
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 click here.
Refund Policy: If there’s 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 About Fix Flex (Fish Flex) Cephalexin 250 mg / 500 mg
What is Fix Flex (Fish Flex) and who is it for?
Fix Flex, also known as Fish Flex, is a cephalexin fish antibiotic in capsule form made for ornamental aquarium fish and non-food pet birds. It is not intended for people or for animals raised for meat, eggs or other food products.
Is Fix Flex the same as “cephalexin for fish”?
Fix Flex cephalexin capsules contain cephalexin monohydrate, an antibiotic commonly used by aquarists when fish show signs that are consistent with bacterial problems, such as fin and tail damage, skin sores or red patches. It is formulated and labeled for aquarium use, not as a substitute for prescriptions for humans or other pets.
Can I use Fix Flex for myself, my dog or my cat?
No. Fix Flex cephalexin capsules are for aquarium fish and non-food pet birds only. They must not be used for people, dogs, cats or other mammals. If you suspect an infection in yourself or another animal, contact a medical or veterinary professional instead of using fish antibiotics.
When is Fix Flex typically used in fish?
Aquarists commonly reach for Fix Flex when fish develop signs that may point to a bacterial issue, such as frayed fins, fin and tail rot, open sores, red streaks, or swollen areas, and a professional suspects a bacterial cause. Because many fish diseases look similar, it is best to discuss any treatment plan with an aquatic veterinarian when possible.
Does Fix Flex treat fungal or parasitic infections?
No. Fix Flex contains cephalexin, which is an antibiotic that targets certain susceptible bacteria. It does not treat fungal or parasitic conditions. For white fuzz, cotton-like patches, visible worms or other non-bacterial problems, ask an aquatic professional about appropriate antifungal or antiparasitic options.
Can Fix Flex be used for pet birds as well as fish?
Fix Flex is designed first as a cephalexin fish antibiotic. For non-food pet birds, it should only be used under direct guidance from an avian veterinarian who can confirm that cephalexin is appropriate, calculate the correct dose, and specify the route and length of treatment.
How do I choose between the 250 mg and 500 mg capsules?
Fix Flex is available in 250 mg and 500 mg strengths to suit different aquarium volumes and treatment plans. Use the strength and number of capsules recommended on the product label or by your aquatic or avian professional. Do not change the dose or frequency on your own.
How long does it take to see improvement?
Some fishkeepers report seeing early changes within several days once water quality is corrected and Fix Flex is used as directed. The actual timeline depends on the species, the severity of the problem and overall husbandry. Always complete the full course recommended on the label or by your veterinarian instead of stopping as soon as fish or birds look better.
Will Fix Flex affect beneficial bacteria or invertebrates?
Any antibiotic, including cephalexin, may also impact beneficial filter bacteria if it is overused or dosed incorrectly. Monitor ammonia and nitrite during treatment and perform partial water changes as needed. For tanks with sensitive invertebrates or corals, many aquarists prefer to treat fish in a separate hospital or quarantine tank rather than in the main display.
Is Fix Flex safe for both freshwater and saltwater aquariums?
Fix Flex cephalexin capsules are used in both freshwater and marine systems for ornamental fish, following label directions and professional advice. In any setup, keep a close eye on water parameters and tank inhabitants, and stop treatment and seek help if fish or invertebrates show worsening stress.
What should I do if there is no improvement or symptoms return?
If fish or birds do not improve, or if signs return soon after using Fix Flex, stop treatment and consult an aquatic or avian professional. A culture test, a different antibiotic or a completely different type of treatment may be needed. Avoid repeating or extending courses of cephalexin on your own, as this can contribute to antibiotic resistance.
How should I store and dispose of Fix Flex cephalexin capsules?
Store Fix Flex in the original, tightly closed container in a cool, dry place, away from direct sunlight and out of reach of children and animals. Follow local regulations for disposing of unused capsules; do not flush them down the drain or discard them in aquarium water.
More Fish & Bird Antibiotics
Need another aquarium fish or pet bird antibiotic? Explore our Fish & Bird Antibiotics Collection for more Fix line and related treatments.
Looking for dosing and water-care advice? Visit the Fish & Bird Antibiotics Blog for practical guides and treatment tips.
