Starfish Tank Size: Why 2.5 Gallons Isn't Enough

No, a starfish cannot be in a 2.5-gallon tank. Starfish require a much larger tank, with a minimum recommended size of 20 gallons. This is because starfish need plenty of room to move around and explore, and they also need a lot of water to filter-feed on their food. In a 2.5-gallon tank, the starfish would quickly become stressed and could eventually die.