Invertebrate atlas

Geographical Origin and Habitat: The Mushroom Coral (*Discosoma nummiforme*), also known simply as the Disc Anemone, is an incredibly prolific, hardy Corallimorph natively endemic to the warm, sheltered lagoons, calm back-reefs, and deeply shaded overhangs of the Indo-Pacific Ocean. Their natural biotope is defined by low-energy environments and nutrient-rich waters, where they rapidly colonize expansive sections of lower-light reef slopes, forming massive, dense, overlapping carpets of soft tissue over the rockwork.

Taxonomy: Scientifically classified within the Corallimorpharia order, they occupy a unique evolutionary space directly between true sea anemones and stony corals. They entirely lack a rigid calcium carbonate skeleton. Morphologically, they consist of a short, muscular stalk attached to the rock, topped with a broad, flat, fleshy oral disc (resembling a mushroom cap). Unlike true anemones, their tentacles are reduced to tiny, decorative bumps or warts covering the disc surface.

Social Behavior: They are sessile, non-aggressive, but highly territorial space-occupiers. They do not possess the potent, stinging nematocysts of true anemones or *Euphyllia* corals, meaning they rarely physically sting their neighbors. However, they are relentless colonizers. They reproduce and expand their colony with extreme rapidity, physically growing over, smothering, and shadowing slower-growing stony corals and zoanthids in a biological strategy of spatial dominance.

Coloration and Sexual Dimorphism: Sexual dimorphism is non-existent as they reproduce primarily through asexual cloning. Their coloration is staggering in its diversity and intensity, making them a staple of the marine hobby. The fleshy disc can present in solid, striped, or mottled patterns of brilliant neon green, deep sapphire blue, vibrant red, purple, or metallic teal. Under actinic blue aquarium lighting, the entire disc frequently glows with intense, radioactive fluorescence.

Tank Setup: The aquarium architecture MUST accommodate their preference for lower energy environments. Even a 10-liter (2.5-gallon) pico-reef is perfectly suitable.

CRITICAL REQUIREMENT: They MUST be placed in the lower half of the aquarium, in shaded or semi-shaded areas (under rock overhangs or ledges). If placed directly under intense, modern LED reef lighting, they will bleach, shrink, and perish. They strictly require low to moderate, gentle water flow.

Diet and Feeding: They are highly autotrophic and exceptionally easy to sustain. The vast majority of their nutritional needs are met through photosynthesis performed by the symbiotic zooxanthellae living within their fleshy discs. They DO NOT require direct target feeding. While some large Corallimorphs (like *Rhodactis*) will fold up to eat meaty foods, *Discosoma* generally do not. They absorb dissolved organic nutrients directly from the water column, thriving in slightly "dirty" water.

Water Quality: They are universally considered the most indestructible, beginner-friendly "coral" in the entire marine aquarium hobby. They demand stable tropical heat (24-27°C / 75-81°F). Specific gravity (salinity) MUST be maintained between 1.023 and 1.025. They require hard, highly alkaline water (pH 8.1 - 8.4). They actively prefer water with detectable Nitrates (5-15 ppm) and Phosphates; they will frequently shrink, pale, and starve in ultra-low nutrient (ULNS) SPS-dominated systems.

Compatibility and Tankmates: Compatibility requires strategic isolation to prevent them from becoming an invasive weed. They are entirely peaceful toward fish and invertebrates.

CRITICAL WARNING: Do NOT place them on your main, central rock structure. Because they reproduce so rapidly, they will quickly carpet the entire structure and smother expensive stony corals. It is highly recommended to isolate them on a separate "Mushroom Island" on the sand bed, where they cannot easily spread to the main reef.

Aquarium Breeding: Breeding (propagation) is automatic, relentless, and requires zero intervention from the aquarist. They reproduce primarily through asexual pedal laceration; as the mushroom slowly moves across the rock, it leaves tiny fragments of its foot behind. Each fragment rapidly grows into a perfect, miniature clone of the parent. Aquarists can also force propagation by simply cutting the mushroom in half with a razor blade directly through the central mouth; both halves will regenerate.

Risks and Diseases: The absolute greatest risk to *Discosoma* is excessively high water flow; if blasted with strong currents, they will detach their foot from the rock and float aimlessly around the tank until they are sucked into a powerhead and pureed. The second risk is excessively intense lighting, causing lethal bleaching. The third risk is the coral becoming an invasive pest, multiplying out of control and smothering the entire aquarium if not properly isolated on a separate rock.