A reader asked us an interesting question recently about some red worms in his fish tank. Although his question is preceded by some background information, he is primarily concerned with how long red worms can live under water in a fish tank. Since red worms are earthworms, his basic question is this: how long can earthworms live under water? Indeed, since earthworms are very often referred to simply as “worms,” his question can be made more simple still: how long can worms live under water? We explore both this general question and the reader’s specific concern below.