Fish Pen™ (Penicillin V Potassium) from Thomas Labs is an antibiotic that exerts a bactericidal action on gram-positive and some gram-negative bacteria in fish. This fish antibiotic is useful for control of some common bacterial diseases in fish, including diseases caused by bacteria such as fin and tail rot and Flexibacter infections.
Penicillin V Potassium………………250 mg
Add 1 tablet (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.