Glass anemones are small anemones that frequently turn up in salt-water aquariums. They are not a desirable species for an aquarium because they quickly out-compete other invertebrates and take over the tank. They are small anemones, usually about 1-inch long, although large individuals may exceed 2 inches in length. They consume zooplankton and other organic debris, which they digest with the help of symbiotic algae.

Some hobbyists establish an isolated colony of these anemones inside an aquarium to help remove some of the nutrients from the water. This is a risky, if sometimes worthwhile, procedure, and care must be taken to prevent the isolated anemones from escaping. Screens should cover all sides of the isolation tank and pump inlets. The anemones are regarded as hardy organisms that are likely to thrive in any tank in which they become established, unless deliberate measures are taken to eradicate them.

Unlike many anemones commonly kept in aquariums, glass anemones inflict painful and damaging stings on other tank inhabitants. They deliver these stings by means of small cells called nematocysts. Glass anemones are one of the 17 species in the genus Aiptasia. They are very prolific anemones, and a single animal can produce a large number of juveniles each day.