Marine aquarists looking for a gorgeous, interesting, nano-friendly fish might entertain the idea of keeping the purple firefish (a.k.a. the purple dartfish, elegant firefish/dartfish, and decorated firefish/dartfish, among various other common names). Given appropriate tankmates and care, this graceful, hardy, relatively undemanding denizen of the Indian and western Pacific oceans can prove to be a worthy resident in a peaceful FOWLR or reef aquarium.
Potentially reaching around 3.5 inches in total length, the purple firefish (Nemateleotris decora) has a slender, torpedo-shaped body with elongated second dorsal and anal fins. This fish’s fins could be said to vaguely resemble the fins of a dart, and its slender body the shaft of the dart—hence the “dartfish” moniker. Its coloration is yellow to white overall with a swath of purple extending from the snout along the dorsum to the first dorsal fin. The unpaired fins are a stunning purple and burgundy.
N. decora is a zooplanktivore that feeds primarily on tiny crustaceans and their larvae. Captive specimens will accept most appropriately sized meaty foods drifting in the water column. Mysids, enriched brine shrimp, and finely chopped mollusk or crustacean flesh are all good choices. Offer several small feedings per day rather than one large meal. Also, occasionally enriching foods with a nutritional supplement is recommended to maintain this species in optimum health and coloration.
The purple firefish is a good candidate for smaller marine systems, with a 20-gallon tank being appropriate minimum housing. This species spends most of its time hovering in the water column, in a slight tail-down orientation, close to a safe retreat, so be sure your live rock is arranged to provide ample nooks and crannies for hiding. Being a notorious jumper, N. decora also demands a well-covered aquarium—especially when it’s just getting settled in.
Peaceful, non-boisterous companions are in order for N. decora. Aggressive or overly active/competitive tankmates will drive this skittish species into hiding and prevent it from getting its fair share of food, potentially to the point of starvation.
In photographs, N. decora is very commonly depicted swimming in pairs. However, it’s important to keep in mind that this should be attempted only with known mated pairs (i.e., male/female bonded pairs that were collected together). Otherwise, conspecifics kept in the same tank are likely to squabble with one another.
Being small, peaceful (toward heterospecifics), not prone to copious waste production, and completely disinclined to nip, nibble on, or otherwise consume corals and other sessile invertebrates, N. decora makes an ideal candidate for reef systems—again, with the caveat that any piscine tankmates are very peaceful and not overly energetic.