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Fish Pen (Penicillin)

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Product Overview

How To Use

What’s in it?


Questions & Answers

Product Description

Fish Pen is an antibiotic that uses penicillin to treat infections associated with gram-positive and certain gram-negative bacteria.

What is Fish Pen (Penicillin)?

Fish Pen (Penicillin) is an antibiotic effective against pathogenic bacteria associated with ornamental fish diseases.

Who is Fish Pen (Penicillin) for?

For use in aquarium, ornamental, and exotic fish.

Why use Fish Pen (Penicillin)?

Fish Pen works in your aquarium to treat skin ulceration, columnaris disease, gill disease, tail rot, fin rot, eye infections, and pop-eyes.

How does Fish Pen (Penicillin) work?

Penicillin is an antibiotic with bactericidal action against gram-positive and some gram-negative bacteria,


Thomas Laboratories

Active ingredient(s):


How is Fish Pen (Penicillin) sold?

Fish Pen (Penicillin) is sold as tablets in strengths of 250 mg or 500 mg in 30 count, 60 count or 100 count.

What special precautions are there?

  • Not for use in fish intended for human consumption.
  • Keep out of reach of animals and children.

What to do if overdose?

Contact your closest emergency animal hospital.

How can I store Fish Pen (Penicillin)?

Store in a dry and cool environment. (15°-30°C).(59°-86°F)

Helpful Tips:

Keep lid closed tight.


Dosage & Administration: Add one tablet (250 mg) into aquarium for each 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 the infection, it is recommended that extended baths in the medication continue for a minimum of 5 days & for not more than 10 days. Discontinue treatment with this medication if no improvement is noted within 5 days.

Main Ingredients


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Fish Pen (Penicillin)

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