Care
Mushroom Polyps, or Mushroom Rocks as they are often labelled in the shops, are a large and varied group of corallimorpharians that are extremely popular with the marine aquarist on account of their multitude of colours, patterns, iridescent and fluorescent hues, their ease of keeping, and their willingness to readily reproduce. The name corallimorpharian literally means "corals without a skeleton", and as such they are often referred to as "false corals". Within the order Corallimorpharia, sit 4 families: Corallimorphidae, Discosomatidae, Ricordeidae, and Sideractidae. Mushroom Polyps from the Actinodiscus and Discosoma genera are classified within the family Discosomatidae. The Discosomatidae are all solitary polyps, which are largely colonial in nature. Classification beyond genus level is very difficult; the taxonomy of the various species is currently in a real state of flux, and is likely to be revised as more research is carried out.
Although Mushroom Polyps are quite widespread in the wild, the vast majority are found in mid-depth waters and often in areas of the reef that are somewhat shaded, for instance between large coral heads or pieces of rubble. Just a handful of species are found in much shallower waters. Mushroom Polyps are small, non-predatorial animals that gain their nutrients through direct uptake from the water, from ciliary mucus transport of trapped particulate matter, and from their symbiotic zooxanthellae. These animals do possess nematocysts, but these are very rudimentary and are incapable of trapping all but the smallest pieces of particulate matter. In the home aquarium, Mushroom Polyps do not respond well to intense lighting or vigorous currents; indeed, fluorescent lighting and low currents seem key in providing the ideal conditions for them to thrive. If your system is very brightly lit, Mushroom Polyps are best placed low in the tank, or underneath an overhang in the rockwork where they will be more shaded. If they are sited in an area that is too brightly illuminated, this tends to cause the zooxanthellae to multiply far too rapidly, overwhelming the natural pigmentation and resulting in very brown coloured mushrooms. As these corallimorpharians are semi-aggressive by nature, ample space should be left between them and other cnidarians, as they will spread rapidly under good conditions, and may encroach upon and attempt to overgrow other sessile invertebrates. Some aquarists find the addition of iodine supplements are beneficial to these animals, whereas others find that providing small frequent water changes and a regular feeding regime is better. It is a good idea to quarantine new Mushroom Polyps for several weeks before adding to the main aquarium, to lessen the chance of introducing any pests such as flatworms. If this is not an option then a coral dip can be useful before adding new polyps to the display tank. Mushroom Polyps are excellent species for beginners.
Feeding
Zooxanthellate, but benefits from supplemental feeding with small particulate material such as phytoplankton, marine snow, and occasionally newly hatched baby brineshrimp.
Propagation
Actinodiscus spp. reproduce readily by budding from the parent colony. Can be fragged, but the easiest way to propagate is to simply let the colony grow over onto small pieces of adjacent rockwork.
