Keep your underwater companions comfy. Each purchase comes with Marineland Eclipse Rite-Size Z Filter Cartridges, 3 count & the Marina Floating Thermometer with Suction Cup for Aquariums. The cartridges mechanically filter water through a pad of double thick poly-fiber, trapping debris and waste particles before the water is chemically filtered through Black Diamond Premium Activated Carbon. They are made with a unique ribbed backing to ensure even distribution of activated carbon—and maximum water-to-carbon contact—for crystal clear and clean water. The thermometer is accurate, easy to read and provides temperature readings in both Celsius and Fahrenheit. There is also a clearly marked safety zone that shows the ideal temperature range for most tropical fish. It works in both freshwater and saltwater tanks and is designed to float in a vertical position—but includes a suction cup if you prefer to attach it to the aquarium wall.