Baltic isopods live on the bottom of the seabed, between seaweed and eelgrass, and haul oxygen out of the seawater. They eat rotting seaweed. You can also find them on the beach between washed up seaweed. There are various species of isopods that are difficult to tell apart. They are usually best recognized by the shape of the hind shield. Baltic isopods have three thorns on their tail plate.