Aiptasia
Aiptasia, or also know as glass or rock anemones are the ultimate hitchhiker in saltwater aquariums! So much so that every aquarist will encounter them no matter what precautions they take. If you try to remove them with a knife spores are released which spreads the Aiptasia even more.They are effective filter feeders, but they can sting fish, invertebrates, and corals while taking over precious space in a tank. You can take control of them naturally with Peppermint Shrimp or Aiptasia Eating File Fish, or try Red Sea's Aiptasia-X!