Penn-Plax presents the Pro Balance line of Vacation Fish Feeder Blocks. Worried about finding a fish-sitter as you plan for your next weekend getaway or adventure? Or, whenever or not they?ll overfeed your fish? Fear no more! These Fish Feeder Blocks will feed your fish while you?re away. Each block feeds to up 3 days, and each package contains 4 Starfish Shape Blocks. Safe for Freshwater and Saltwater fish. Ideal for 10 - 15 Gallon Tanks: Our Fish Feeder Blocks work best in aquariums that are between 10 and 15 Gallons in size. One block will last 3 to 4 days depending on the PH level and water temperature. A minimum water temperature of 72°F (22°C) and PH level of 6.6 to 7.0 is most efficient for the release of food particles. Requires Aeration & Circulation: Within hours, our Feeder Blocks will start to dissolve, releasing nutritious freeze-dried foods while neutralizing your aquarium?s water. In order for this to happen, your tank should have the proper aeration and circulation. Our Feeder Blocks dissolve normally with setups that have an air stone or filter. Give It a Try before Your Trip: Just like us, our fish can get picky over their food. As a suggestion, you may want to place 1 Feeder Block in your tank a week before your vacation or trip. This way, you?ll see if they like it or not. To take it a step further, you may want to leave the tank alone as you test our Feed Blocks, mimicking the trip. Ingredients: Calcium Sulfate, Freeze-Dried Tubifex Worm, Freeze-Dried Bloodworm, Freeze-Dried Daphnia, Freeze-Dried White Shrimp, Thiamine Mononitrate (Source of Vitamin B1), and Pyridoxine Hydrochloride (Source of Vitamin B6). Shop Penn-Plax for All Your Pet?s Needs: Penn-Plax is a manufacturer and distributor of top quality pet supplies, who specialize in creating excellent pet products for animals, both great and small.