Knobby Fancy Brittle Sea Star

Ophiomastix annulosa

Saltwater Invertebrate Species Group: Starfish Family: Ophiotrichidae

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Water parameters

Temp 76-80 F Temperature

Maintaining a stable and appropriate temperature is critical for the survival of aquatic life.

pH 7.8 - 8.4 potential of Hydrogen

Measuring the acidity or alkalinity of water on a 0–14 scale, where 7 is neutral, 7 is alkaline.

NO3 1-20 ppm Nitrate

While less toxic than ammonia, high nitrate levels (above 40–80 ppm) are important to monitor because they can cause fish stress, stunted growth, and harmful algae blooms.

NO2 <0.0001 ppm Nitrite

It is a highly toxic, intermediate compound in the nitrogen cycle produced from broken-down ammonia

PO4 0.01 - 0.1 ppm Phosphate

It is essential for plant development but must be managed, as excess levels trigger nuisance algae blooms and inhibit coral calcification.

NH3 <0.1 ppm Ammonia

It is the primary killer of aquarium fish, causing gill damage, stress, and death

Ca 380 - 450 ppm Calcium

Supporting the growth, skeletal structure, and shell formation of corals, mollusks, crustaceans, and coralline algae

KH 8 - 12 dKH Alkalinity

It acts as a shield, neutralizing acids to prevent dangerous pH "crashes" that can harm fish, corals, and plants.

Mg 1200 - 1400 ppm Magnesium

It enables coral growth by supporting skeletal formation, assists in metabolic processes, and ensures that calcium is available for corals, clams, and coralline algae.

SG 1.023 - 1.026 SG Salinity

Essential for maintaining stable, natural water parameters, proper osmoregulation, and stress-free environments for marine fish and corals

ORP 250 - 400 mV Oxidation-Reduction Potential

A higher positive mV indicates clean, oxygen-rich water with high water quality, while low readings indicate high pollution.

About Knobby Fancy Brittle Sea Star

General information

The Knobby Fancy Brittle Sea Star, or Chain-Link Brittle Star, has a very small red central disc which may have variable patterns. The long, elegant arms are fringed with fancy paddle-shaped spines and among shorter sharp spines. It is nocturnal and often hides under rocks during the day. At night, it comes out to eat detritus and small organisms. Avoid housing with slow, small, sluggish fish. The Knobby Fancy Brittle Sea Star is very intolerant of sudden changes in oxygen levels, salinity and pH of the water, and cannot tolerate copper-based medications. The drip acclimation method is highly recommended for all Sea Stars due to their intolerability to changes in water chemistry. It should never be exposed to air while handling. Ophiomastix annulosa is reported to possess toxic mucus capable of paralysis and fatality in small animals. Always use caution when handling, and avoid any contact with eyes or mouth.

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