Bubble mushroom, Warty mushroom, St. Thomas mushroom, Atlantic Bubble Mushroom, Warty Corallimorph all equal Discosoma sanctithomae.
A write up from Animal World.
"The Discosoma sanctithomae, most commonly known as the Bubble Mushroom or Warty Mushroom, is named for the shape of its tentacles. It is also known as the Atlantic Bubble Mushroom, Warty Corallimorph, and St. Thomas Bubble Mushroom. It is a well known and favorite mushroom coral, offering a distinctive look to the reef aquarium.
This is a larger mushroom, and can grow to 4" (10 cm). One of its unusual characteristics is that it will sometimes close part way, into a "purse-string" style, and quickly capture an unwary fish seeking to hide in the "enclosure". Their tissue is very thin however, and can tear easy.
The Bubble Mushroom usually comes in translucent green, blue, yellowish green, purple-mauve, green, brown and orange with tentacles that may contrast in color and be iridescent. Instead of having long feeder tentacles, their tentacles will form rounded vesicles or they may elongate to take on a fuzzy appearance. Like other mushrooms, the tentacles do have toxins in them.
This mushroom is very decorative and moderate to easy to care for, but it is a more expensive mushroom coral. The Bubble Mushroom is a good choice for Metal Halide lit tanks, since it likes indirect intense lighting. You may have to experiment on locations for maximum size, color and reproduction. They are a bit more difficult than the Actinodiscus genus because they are not as tolerant of poor water conditions. They also cannot handle a high water flow since it will prevent them from getting nourishment.
The D. sanctithomae propagates easily in captivity, which can contribute to preserving the wild populations. After splitting however, the clone mushroom doesn't necessarily always resemble the "mother" mushroom, thus giving the aquarist a variety of shades and colors. They have very few predators if any."
