Keep your tank healthy and thriving with the Fritz Aquatics Mardel Maracyn Two Antibacterial Aquarium Medication. The fast-dissolving powder formula uses maracyn-two, an advanced broad-spectrum antibiotic to treat common bacterial infections including body fungus, gill disease, popeye, tail and fin rot, and dropsy. It works in both freshwater and saltwater fish, and helps treat common symptoms like clamped fins, swollen eyes and patchiness. Plus, it won’t harm invertebrates so you can use it around shrimp and other antenna-wearing aquarium buddies.