Bio-Tet is a medicated tablet designed to treat bacterial infections in both freshwater and marine aquariums, especially those caused by bacteria that are sensitive to tetracycline. It is effective for treating fin rot, ulcers, cloudy eyes, mouth fungus, and similar bacterial conditions. The tablets also help in managing red slime algae (cyanobacteria) outbreaks. Typical dosage is one tablet per 20 litres of aquarium water, and water may turn red during treatment—a sign it is active—with the colour fading after about one week. Prolonged use can negatively impact beneficial bacteria in biological filters, so caution is advised.