Red Mushroom, Metallic Red Mushroom, Actinodiscus cardinalis
Actinodiscus cardinalis

The Red Mushroom is an exotic beauty that will make a prize showpiece in your aquarium!.

The Red Mushroom or Metallic Red Mushroom A. cardinalis is a very pretty addition to your display. Red is not a common color in aquaria, well at least true red, since most reds border on orange or brown. These mushrooms are a welcome member, taking out nutrients that we don’t want in our system, as well as adorning an area of rock with their beautiful red coloring. Keeping them in check is easy, if you provide sand a barrier around the rock they are on and keep them at least 6″ from the main rock work.

Though a bit costly to acquire, the A. cardinalis is very hardy and one of the best corals for both beginners and advanced aquarists. They are easy to care for and they don’t like or need high levels of light. In nature they primarily feed off suspended micro particles from the water column. There is no need to feed them in captivity as they will take what nutrients they need from the water.

Besides their impressive coloring, the Red Mushrooms reach only 2-3″ (5-8 cm) in diameter. Small and compact, they are a great addition to any nano tank, or to larger sized aquariums as well. The A. cardinalis also propagates easily in captivity. They are semi-aggressive. If they are near another coral they will cause them to loose tissue, recess, and possibly die. Acroporas will not grow in aquariums with large mushroom populations. A. cardinalis have very few predators if any.

Red Mushroom, Actinodiscus nummiformis var. cardinalis

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Calming video of a Red Mushroom eating

Kick back, grab a cup of coffee or tea or whatever relaxes you and enjoy the music as you watch the Red Mushroom do mushroom things. The Red Mushroom is yet ANOTHER variation of Actinodiscus nummiformis, although some use the unaccepted name A. cardinalis. Like other A. nummiformis, the Red Mushroom can have a wide variety of texture on the surface and can even have stripes! Sometimes the baby bud that pops up is a different color! Easy to care for with low light needs, this is a great beginner coral for 1 gallon and up!

Scientific name

Family: Discosomatidae

Species: Actinodiscus cardinalis

Distribution / Background

Mushroom Coral Information: The Red Mushroom or Metallic Red Mushroom Actinodiscus cardinalis was described by Ruppell and Leuckart in 1828. Some general names for these are Mushroom Coral, Mushroom Anemone, Disk Anemone, Mushroom Rock Actinodiscus, Coral-like Anemone, False Anemone, Jewel Anemone, Shroom, and Mushroom.

As far as current taxonomy, the A. cardinalis is listed under Actinodiscus and not Discosoma, according to the 2007 taxonomy list. The taxonomical identification of mushroom corals has a history of limited and dated information which is often of dubious value and sometimes incorrect. Mushrooms corals have no fossil records and studying the physical aspects has proved to be not very reliable for identification. Modern methods using DNA and RNA testing to deduce the sequence of genes, though more reliable, is not readily available.

Where Mushroom Corals Are Found: The Actinodiscus cardinalis are found in the South Pacific and the Indo-Pacific oceans.

Mushroom Coral Habitat: The Red Mushroom prefers low current, and shallow to mid-depth waters. Some are found in shallower brighter waters as well. Like other mushrooms, they prefer the shaded areas, indirect sunlight, where they like to grow on dead corals, rubble, and between coral heads. They feed on micro particulate items in the water column.


The Actinodiscus cardinalis is not on the IUCN Red List for endangered species


What do Mushroom Corals look like: These Coral Mushrooms Actinodiscus cardinalis are basically a coral without a skeleton and their internal structures are the same as stony corals. The top of their body or the upper surface is called the oral disc. The stalk area, which is very small, is called the column and it is located just above the pedal disc, which is where they attach to surfaces.

The A. cardinalis can be various shades of red from a burgundy or dark red to red. They can also have striated surfaces (small shallow grooves radiating from the center) as well as pimpling and at times, thin white bands here or there, running from the center to the edge.

Though they lack the long feeding tentacles to capture prey, their surface does hold several types of stinging cells. They can actually warp the surface of their oral disc to change the water flow over them to direct particulate and flocculent material toward their mucous center for absorption. At times they will make a trumpet shape. This is thought to be formed when they are needing nourishment, or if the light level is low, or is of low quality due to age.

Mushroom Coral Life Cycles: The Red Mushroom can grow to 2-3″ (5-8 cm), but their life span is unknown.

Difficulty of Care

Mushroom Coral Care: The Red Mushroom is easy to care for and does not like or need high levels of light. They should be kept in shaded areas in tanks with high output lamps. If they are not shaded, they turn all brown and fail to thrive. Some will just float around the tank until they find a nice shaded area or have an unpleasant encounter with a pump. They also cannot handle high or high to moderate water flow. But they can handle higher levels of nitrate than SPS and LPS corals.

Foods / Feeding

Mushroom Coral Feeding: The Red Mushroom is a carnivore. In the wild, these corallimorphs are well equipped with nutritional alternatives for their well-being. They derive nutrition from their symbiotic algae, zooxanthellae, that dwells within their tissues and they eat suspended micro particles out of the water column. They can actually warp their surfaces to change the water flow over them to direct particulate and flocculent material toward their mucous center for absorption.

In captivity you can feed your A. cardinalis newly hatched artemia once in a great while. But really, it is the nutrient level in your tank that they will thrive in, and not direct feedings.

Aquarium Care

Water changes of 10% bi-monthly or 20% a month are typical. Provide a reef environment with proper magnesium levels. Some claim proper iodine levels are beneficial also. Due to their toxins, active carbon is a good idea with larger colonies of mushrooms. Do not over skim since the A. cardinalis need nutrients to survive on and will not do well in a pristine environment.

Aquarium Parameters

A typical live rock/reef environment is what is needed for your Red Mushroom. Provide rubble or dead coral and live rock for them to have something with which to attach their pedal disc. They do not do well with strong water movement, so direct the power heads and intake nozzles away from them. As they can float around when looking for a place to settle, it’s a good rule of thumb to have all of your pumps covered. Most good quality pumps have guards on them.

  • Minimum Tank Size / Length:Nano tank of 1 gallon or more
  • Marine Lighting: Low
  • Temperature: 72° – 83° F (22° – 28° C)
  • Salinity / Specific Gravity: 1.023 to 1.025
  • Water Movement: Low / weak
  • Water Region: Bottom of the aquarium

Compatibility and Social Behaviors

The Red Mushroom is semi-aggressive if they are near another coral. They will cause other corals to loose tissue, recess, and possibly die. Acroporas will not grow in aquariums with large mushroom populations. Make sure to leave 6 – 8 ” between your mushrooms and other corals. Watch the growth rate since the A. cardinalis will overgrow and kill any nearby corals.

Mushroom Anemones will tolerate their own species and usually other Mushrooms. In the wild many species of Mushroom Corals occur together in large groups. In captivity A. cardinalis will get along with their own species, but may not tolerate mushroom species outside their colony. Even in one genus, if the color is different or a different species, the weaker mushroom will detach and find another location. Strong water movement will cause them to detach as well.

Sex – Sexual differences

No sexual difference in appearance is known.

Breeding and Reproduction

  • Mushroom Coral Reproduction:
    Corallimorphs reproduce in 4 different ways. The first three ways, asexual budding, laceration, and division/fission, are successful in the aquarium as most hobbyists soon discover. Budding is where individuals are formed from particles divided off from the pedal disc. Similar to budding, laceration happens when they move slowly over the surface and leave behind small pieces that will eventually form into mushrooms. Division or fission is where an individual divides down the center and forms two animals.
    Sexual reproduction is where eggs and sperm are released into the water column. They unite and form free-swimming larvae which are initially plankonic, and them settle and adhere to the substrate. Sexual reproduction has not been well documented, and has not been observed in captivity. Presumably modern filtration methods are inhospitable to free swimming larvae.

  • Mushroom Coral Propagation:
    Mushroom corals can be easily propagated in captivity by cutting individual polyps into several pieces. Placed the pieces on a gravel substrate with low water flow. They will attach themselves to pieces of gravel. Later they can then be super glued to a suitable substrate such as a reef plug. It has been stated that the warmer end of their temperature spectrum encourages reproduction.

For details on how to propagate your mushroom corals see Mushroom Corals: Mushroom Coral Propagation

Potential Problems

The A. cardinalis are disease resistant, and only affected by improper husbandry. Problems for the most Corallimorphs are pretty minimal unless your lighting, water movement, feeding and water quality are improper for these animals. A sign of this is if your coral mushroom detaches to look for “better conditions” to settle in. They have very few predators if any.


Mushroom Corals for Sale: The Red Mushroom or Metallic Red Mushroom A. cardinalis can usually be found online and at pet stores, as well as from frag farmers and most reef clubs. Online they are $39.00 USD or more depending on the size of the rock they come on and their color.


Featured Image Credit: vojce, Shutterstock