Something a little quirky are the Hydrocorals, a Fire Coral or Lace Coral can literally ‘spice’ things up!

   The well-known hydrocorals include the Fire Corals in the Milleporidae family and the Lace Corals in the Stylasteridae family. They are Cnidarians just like the stony corals, but are in the class Hydrozoa.

   When diving, snorkeling, or keeping Fire Corals in the aquarium you want to be very careful. The Millepora genus has a potent sting. It may be just a mild sting for some people, but can cause anaphylactic shock in others. Needless to say, wear gloves when you are handling or anywhere near the coral. Don’t be dissuaded from keeping them because of their sting, since they are hardy and easy to propagate, just be careful and wear gloves.

For more about hydrozoans, see:
Introducing the Class Hydrozoa: Fire Corals, Lace Corals, Hydra, Jellyfish and More

Family: Milleporidae – Fire Corals
Click for more info on Fire Coral
Millepora alcicornis

Family: Stylasteridae – Lace Corals
Click for more info on California Hydrocoral
Stylaster californicus

Class Hydrozoa

   There are many animals in the class Hydrozoa, but only a few hydrocorals like the Fire Corals and Lace Corals are found in the aquatic industry, along with some small hydroid polyps. These small polyps can inadvertently show up as aufwuchs on invertebrates and plants, but are short lived in the aquarium.


  Hydrocorals are not true stony corals, they are actually more like a very hard “soft” coral. Yet the Fire Corals are very similar in appearance and habitat to stony corals, and they are also hermatypic. This means they contribute to reef building, creating a hard skeleton from calcium absorbed from the water. The Lace Corals will also produce an aragonite and/or calcite skeleton but are mostly small, “lacy”, and very delicate.

Familiar Hydrozoa

   Besides the Fire Corals and Lace Corals, there are some other well-known and familiar hydrozoans.

  • Hydra
    The Hydra, introduced to high school students in their biology class, is a small solitary freshwater hydrozoan polyp. But it may not be the best example of this class since it does not incorporate all the complexities this animal group possesses.

  • Jellyfish
    Jellyfish are also related to the hydrocorals, with some genera included in the class Hydrozoa.

  • Floating Hydrozoans
    Some other familiar colonial hydrozoans include the so-called Portuguese man-o’ war from the Physalia genera, and the Blue Button Porpita porpita. These animals can sometimes be found washed up on the beach and can be mistaken for jellyfish, but a jellyfish is just a single individual while these hydrozoans are made up of multiple individuals.

Featured Image Credit: Fire Coral by Rob, Wikimedia Commons CC 2.0 Generic