Aqua MedZyme DC Dry Concentrate 1 lb Renders deadly ulcer causing Aeromonas, Pseudomonas harmless to your fish NO REFRIGERATION needed , never worry about keeping your "Zyme" cold again Treats pond water as low as 40 degrees (F) Great for early spring & late fall treatments Can be stored at room temperature for 3 years or more DOES NOT contain chemicals, antibiotics or medications