Midnight (Nox) Dwarf Angelfish

The Midnight (Nox) Dwarf Angelfish (Centropyge nox) is a marine angelfish recognized by a nearly uniform black body and dark fins. Its laterally compressed body allows it to move through reef structure while its patterned fins and deliberate movements create a distinctive display. Natural variation in age, origin, lighting, and individual pattern can affect appearance. Adult care requirements apply regardless of the size at purchase.

Native to Western Pacific, this fish is associated with reef habitat offering shelter, feeding surfaces, and protected routes between rock formations. Its daily activity includes inspecting crevices and picking small food items from established reef surfaces. Its naturally secretive habits make a network of shaded retreats especially valuable.

A healthy adult may reach approximately 3.9 inches (10 cm), so plan a mature aquarium of at least 70 gallons. With suitable space, steady feeding, and appropriate companions, it can become an engaging long-term aquarium resident. Aquarium volume, layout, feeding access, and adult compatibility should be considered together before introducing the fish.

Quick Care Guide

Care Level: Moderate
Minimum Tank Size: 70 Gallons
Adult Size: Up to 3.9 inches (10 cm)
Temperament: Semi-Aggressive
Diet: Omnivore
Reef Safe: With Caution
Region: Western Pacific
Scientific Name: Centropyge nox

Tank Requirements

Provide a fully cycled, well-established marine aquarium with a minimum volume of 70 gallons for adult housing. This is an active rock-associated grazer, so usable rock surface and territory matter more than a small body might suggest. A taller, narrow aquarium should not be treated as equivalent to a broad display simply because the volumes match.

Arrange stable rock formations into caves, overhangs, and connected passages while retaining open water at the front and above the structure. Retreats should comfortably accommodate the adult without forcing it to scrape its sides or fins. Multiple entrances help prevent a dominant tankmate from trapping the fish inside a single cave.

Mature rockwork provides security and places for natural browsing between prepared meals. An aquarium covered in clean, newly installed rock does not supply the same feeding opportunities as an established reef surface. Its naturally secretive habits make a network of shaded retreats especially valuable.

Secure the aquascape before adding livestock. Rest heavy structures on a stable base and leave space for cleaning around them. Although this angelfish does not require a particular substrate, a clean sand bed or a well-maintained bare bottom should allow waste to be removed without repeatedly disturbing its shelters.

Provide efficient biological filtration, regular mechanical waste removal, and an appropriately sized protein skimmer. Frequent feeding increases the nutrient load, and a system that holds acceptable readings while lightly stocked may need additional capacity before a substantial angelfish is added.

Maintain moderate, varied water movement with calmer areas behind the rockwork. Good surface agitation and dependable oxygenation are important, especially overnight. Avoid directing a powerful unbroken jet into the fish's preferred shelter.

Use a secure cover and protect overflow openings. During introduction, reduce disturbance and let the fish choose a retreat. Keep the daily lighting schedule predictable so feeding and resting behavior can settle into a routine.

The stated volume is a starting point for one adult, not an allowance for several competing angelfish. Additional large or territorial residents require more space, more visual barriers, and a practical plan to separate fish if compatibility changes.

Diet and Feeding

The Midnight (Nox) Dwarf Angelfish is an omnivorous reef grazer. Its captive diet should combine algae-based foods with small marine animal foods rather than relying on either vegetable material or meaty food alone.

Natural browsing is useful enrichment, but it is not a substitute for a complete prepared-food routine. Rockwork may look mature while supplying too little nutrition to maintain a newly introduced angelfish.

Offer a balanced selection that includes:

• Sponge-containing marine angelfish preparations

• Spirulina-based marine pellets or flakes

• Marine algae and nori

• Frozen mysis shrimp

• Enriched brine shrimp

• Finely chopped clam or other marine seafood

• Balanced frozen marine omnivore blends

Offer two to three small meals daily, adjusting portions to age, body condition, and the amount of food actually consumed. Growing juveniles and thin new arrivals often need additional small opportunities rather than one oversized feeding. Remove uneaten portions before they collect in caves or around filtration intakes.

Offer algae on a secure clip and place small prepared portions where the fish can approach without being chased. More than one feeding location can reduce competition.

Watch for actual swallowing, not simply interest in food. A fish that repeatedly mouths and rejects every item may still be losing condition. A pinched abdomen, persistent hiding, or an established tankmate intercepting every meal calls for a change in the feeding arrangement.

Once established, many individuals accept a mixture of frozen and prepared foods. Introduce new textures gradually while continuing dependable foods so dietary variety does not come at the expense of consistent intake.

Include a regular vegetable component even when the fish eagerly consumes shrimp. Spirulina foods and marine algae help broaden the menu beyond highly palatable animal foods.

Avoid using unenriched brine shrimp as the sole long-term ration. Freshwater feeder fish and terrestrial meat are unnecessary and poorly matched to this animal's feeding ecology. A varied marine-based menu, suitable portion sizes, and routine observation support long-term body condition.

Do not assume that a fish refusing food will recover simply by being left in a busy display. Reduce competition, check water quality, and provide a calm feeding area when needed. Persistent refusal to eat should be addressed before substantial weight loss develops.

Temperament and Tankmates

The Midnight (Nox) Dwarf Angelfish is best described as semi-aggressive. Territorial behavior is most likely around established rockwork and toward other angelfish with similar shapes, patterns, or feeding habits.

One dwarf angelfish is the most predictable arrangement for an ordinary home aquarium. Mixing several species requires considerably more territory than the minimum size listed for a single fish.

Potential companions include appropriately sized wrasses, tangs, rabbitfish, and robust community fish, selected for the aquarium's actual space and the individual fish's temperament.

Avoid crowding the aquarium with visually similar competitors. Even otherwise compatible species can become difficult neighbors when they compete for the same cave or feeding position.

Introduce new residents thoughtfully. An acclimation box can help evaluate reactions, but behavior during a short introduction does not guarantee permanent compatibility. Ensure the box provides appropriate water movement and does not force the fish into continuous bright light or contact with aggressive tankmates.

Observe interactions at feeding time and near preferred resting sites. Repeated pursuit, torn fins, a fish pressed into one corner, or persistent refusal to leave a cave are signs that the arrangement needs attention. Occasional displays should not be confused with ongoing harassment that prevents normal activity.

Provide visual breaks between territories and keep a separation option available. Aquascaping can reduce encounters, but it cannot make fundamentally incompatible fish safe companions. Adult behavior may become more assertive as a juvenile matures or as a new fish changes the social order.

Do not use a small juvenile's initially tolerant behavior to predict the temperament of the full-grown adult. Plan compatibility around the mature fish and reassess after growth, spawning behavior, or major changes to the display.

Reef Compatibility

The Midnight (Nox) Dwarf Angelfish is reef safe with caution. Some individuals coexist with corals, while others develop repeated picking behavior that makes removal necessary.

Potential targets include fleshy stony-coral tissue, soft-coral polyps, zoanthids, clam mantles, and attached reef invertebrates. Natural browsing can turn into persistent irritation when an individual begins sampling a particular coral.

A fish that leaves corals alone immediately after introduction may change its behavior later. Growth, changing food availability, and individual preferences can alter compatibility even in a previously settled aquarium.

Frequent varied feeding and substantial mature rockwork may provide alternative browsing opportunities, but they cannot guarantee coral safety. Do not purchase a specimen on the assumption that a full stomach will reliably prevent nipping.

Mobile cleanup-crew animals are generally less relevant to its diet than attached reef organisms, but this should not be interpreted as a guarantee for every small or newly molted invertebrate. Observe the actual individual and protect valuable livestock.

If attempting a reef placement, have a practical removal plan before introduction. Moving a fish from elaborate coral rockwork can be difficult, and repeated nipping may prevent a coral from expanding well before obvious tissue loss occurs.

A selected collection of hardy corals does not establish universal reef compatibility. Avoid describing this angelfish as harmless to all SPS, LPS, soft corals, or clams; individual behavior and the animals present determine the result.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Maintain stable marine conditions with undetectable ammonia and nitrite, reliable oxygenation, and controlled nutrient accumulation. Consistent maintenance is especially important in a system receiving the frequent small feedings that angelfish benefit from.

Avoid rapid changes in temperature, salinity, or pH. Steady conditions within an appropriate range are preferable to frequent corrective additions made solely to chase an exact number.

Check salinity with a calibrated instrument and keep top-off consistent. Clean mechanical filtration, remove trapped food, and perform water changes appropriate to the actual nutrient load. Quarantine new fish in a stable, fully supported system, and do not allow a bare treatment aquarium to become a source of ammonia stress.

Acclimate according to the water conditions of the source and receiving system, keeping handling calm and deliberate. Angelfish have cheek spines that can catch in mesh; use suitable containers and careful transfer methods to reduce injury.

Common Considerations

• Adult Housing: Plan for approximately 3.9 inches (10 cm) and at least 70 gallons, with a suitable footprint and additional space when keeping other territorial or active fish.

• Species-Specific Needs: Its naturally secretive habits make a network of shaded retreats especially valuable.

• Reliable Feeding: Provide a varied omnivorous menu and observe actual food intake; mature rockwork supports browsing but cannot replace a complete feeding routine.

• Compatibility: Semi-Aggressive behavior requires suitable companions and monitoring. Corals and clam mantles may be sampled; maintain a removal plan for persistent picking.

• Long-Term Observation: Monitor body condition, breathing, feeding response, and social interactions as the fish grows. A quiet introduction and regular observation help identify problems before they become persistent.