How to Give a Dog Fish Flex

Fish Flex is a brand name for the antibiotic cephalexin. This item can be purchased over the counter online or at a local pet store that carries supplies for pet fish. Antibiotics are used to treat infections. Fish Flex is labelled for aquarium use only. If you have concerns about administering Fish Flex to your dog, you should consult with a veterinarian.

Weigh your dog on a bathroom scale. If your dog is small, the best method for weighing is to first step on the bathroom scale without your dog. Make a note of the weight. Pick up your dog and step on the scale again. Subtract the first weight from the second weight. This is the weight of your dog.

Open the package of Fish Flex. Read the product information carefully. Fish Flex is usually sold in 250 mg caplets. Depending on the weight of your dog, more than one tablet may be required. For very small dogs, the caplets will have to be broken into smaller doses.

Determine the correct dosage for your dog. To determine the correct dosage of Fish Flex to administer, convert your dog's weight from pounds to kilograms. Divide the kilograms by 50. This is the daily dose of Fish Flex for your dog.

Divide the daily dosage into four equal portions. Administer one portion every six hours.

To give your dog Fish Flex, insert the portion into soft cheese. Try to make your dog think she is getting a treat. If this does not work, then take the dosage and gently push it into the back of your dog's throat. Hold the mouth closed and rub your dog's neck until she swallows the medication.

Continue treatment for 14 days or for as long as a veterinarian recommends.


Large dogs should be weighed on a scale that they can stand on comfortably. If your dog cannot have cheese, use peanut butter instead. See if your scale has an option to weigh in kilograms.


Overdoses can lead to death. Diarrhoea is a common side effect of cephalexin. Treat with a probiotic administered with food. Be sure to keep water available at all times.

Things You'll Need

  • Fish Flex
  • Bathroom scale
  • Semi soft or soft cheese
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About the Author

Lynda Altman started writing professionally in 2001, specializing in genealogy, home-schooling, gardening, animals and crafts. Her work has appeared in "Family Chronicle Magazine" and "Chihuahua Magazine." Altman holds a B.A. in marketing from Mercy College, a black belt in taekwondo, master gardener certification, a certificate in graphic arts and a certificate in genealogy.