Fix Pen 500 (Penicillin) Tablets 500mg 60 CountFix PEN 500 Penicillin is effective treatment for pop eyes, infected eyes, fin or tail rot, gill disease, columnaris disease, and skin ulcerations and other bacterial diseases in ornamental Fix. Dosage & Administration: Add one tablet (500 mg) into aquarium for each 20 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