Thomas Labs Fish Flex Cephalexin Antibacterial Fish Medication, 250 mg, 100-count

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Deliver bacteria-busting medicine to your fish with ThomasLabs’ Fish Flex Cephalexin Antibacterial Fish Medication! This broad spectrum antibiotic contains just the right amount of Cephalexin Monohydrate needed to treat bacteria that can plague fish. Fish Flex is flexible enough to handle non-specific pathogenic bacteria commonly associated with ornamental fish diseases. Plus, Fish Flex is designed to work when bacterial infections are most active—treating non-specific bacterial infections during their multiplying stage, so you can catch and cure illnesses quickly!

Key Benefits

  • Made with Cephalexin Monohydrate, a generic form of Keflex that treats non-specific bacterial infections.
  • Halts the multiplication of bacteria typically found in common fish diseases.
  • Broad-Spectrum antibiotic effectively treats many non-specific infections in fish.
  • Easily dissolves in water, creating a medicinal bath that can be used for up to 10 days.
  • This unique formula is developed to work on both saltwater and freshwater fish.

Additional Details

For aquarium and ornamental fish only. Not for human use. This product should not be given to fish intended for human consumption. Keep out of the reach of children and animals. In case of accidental overdose, contact a health professional immediately.

Active Ingredients

Cephalexin Monohydrate 250 mg

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  • Item Number
  • Fish Type
    Betta, Tropical Freshwater, Marine Fish
  • Supplement Form


Add 1 capsule (250 mg) into aquarium for every 10 gallons of water to be treated. Repeat in 24 hours. It is suggested that a partial water change be made between treatments. While duration of treatment depends on type and severity of infection, it is recommended that extended medication baths continue for a minimum of 5 days but not more than 10 days. Discontinue treatment if no improvement is noted within 5 days.

Keep container tightly closed and in a cool, dry place.

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  • My fish feels way better.

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    Noticed my poor fish wasn't eating like normal. A week on the antibiotics and he's mainly back to his old self. What's even better is I didn't have to pay for a vet trip.

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    By on

    Thomas Labs always produce clean,consistent antibiotics.Proven strength.Worth the extra cost.

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  • Product is as advertised

    By on

    Great to have on hand, both for fish tanks as well as other 2 and 4 legged friends.

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