White Spotted Jellyfish

Also called the Australian Spotted Jellyfish, these are native to the Pacific Southwest waters. Fairly large they generally consume snail species but they have become a concern in some areas because of the huge amount of water they filter, digesting plankton that some food fish and other fish need.

White-spotted jellies are one species you don't have to fear. The mild venom isn't a problem for humans. 

These filter feeders are more focused on minuscule zooplankton, and an individual can filter as much as 13,000 gallons of water a day in its quest for a meal

The downside of this is a swarm of white-spotted jellies can clear an area of zooplankton, leaving none for the fish and crustaceans that also make a meal of the microscopic critters. In areas where they are considered an invasive species, such as the Gulf of California, Gulf of Mexico and Caribbean Sea, their voracious appetite poses a problem for native species from corals to shrimp.

The White-spotted Jellyfish is causing a problem overseas, particularly in the Caribbean region. It may have hitched a ride in ships' ballast tanks, travelling from Australia and the Pacific region to the Caribbean. Here, it found an ideal place to breed, free of their natural predators (various Pacific-region snails).