Starfish belong to the class Asteroida. These marine invertebrates are found all over the worlds oceans from warm to cold and shallow to deep waters up to 25,000 feet. Starfish have been recorded to exist over 400 million years which makes them great at survival. Why would you want one in your aquarium? Well, Starfish can be great scavengers taking care of detritus, deceased animals and more. There are also starfish that consume algae. Watching these beatiful and colorful creatures move through the water on their tube like feet is a sight to see!