Purple Firefish (Nemateleotris decora)

You must keep the Purple Firefish either singly or as a single, confirmed male-female bonded pair. This species is widely regarded by experienced reef keepers as the most intraspecifically aggressive member of the genus Nemateleotris. Unbonded individuals housed together will fight relentlessly, often to the point of severe fin damage, starvation-through-stress, or death. If you want a pair, you must purchase two juveniles at the same time from the same system and observe them closely for the first two weeks, or purchase a pre-bonded adult pair from a specialty supplier. A single tank should never house more than one unbonded specimen, and a bonded pair requires a minimum of 30 gallons (114 liters) rather than the 20-gallon (76-liter) minimum acceptable for a single fish.

The absolute minimum is a 20 gallon (76 liter) aquarium for one specimen, with 30 gallons (114 liters) or larger required for a bonded pair. Volume alone is not sufficient. You must prioritize a tank with a footprint of at least 30 x 12 inches (76 x 30 cm) so the fish has enough horizontal swimming room to establish a territory around its burrow and retreat when startled. A tall, narrow nano cube is a poor choice for this species even if the gallonage on paper appears adequate, because Purple Firefish rarely use vertical space and need horizontal sightlines to feel secure.

Purple Firefish are among the most prolific jumpers in the marine aquarium trade. This is an instinctive predator-avoidance reflex, not a sign of poor water quality on its own, although stress and aggressive tankmates make jumping far more likely. You must fit a tight, gap-free lid or a fine mesh screen over every opening, including overflow boxes, power cord cutouts, and skimmer chambers. Any gap wider than approximately 0.2 inches (5 mm) is large enough for this fish to squeeze through. Sudden loud noises, aggressive tankmates, and a lack of secure rockwork burrows are the most common triggers for panic jumping.

The two conditions you must watch for most closely are Marine Ich (Cryptocaryon irritans) and Marine Velvet (Amyloodinium ocellatum), both of which disproportionately affect newly imported Purple Firefish because the species is highly sensitive to the stress of shipping and often arrives in a weakened state. Look for excessive flicking against rock, rapid gill movement, and a dulling of the normally vivid purple and red coloration as early warning signs. You should quarantine every new specimen for a minimum of 2-4 weeks in a bare-bottom quarantine tank before introducing it to your display. Purple Firefish generally tolerate standard reef-safe copper-based and praziquantel-based treatments at label-directed dosages, but you must always follow the manufacturer's dosing instructions exactly rather than estimating, since this species is more sensitive to dosing errors than hardier fish such as damsels or clownfish.