Also Known As: Highfin Perchlet

Compatibility and Behavior
The Geometric Flame Hawk (Plectranthias inermis) is a tiny jewel of a fish with a case of mistaken identity. Despite the name it isn't a true hawkfish at all, but a member of the sea bass family Serranidae, closely related to anthias, though it behaves exactly like a hawkfish. What you notice first is the pattern: a cream to pale body overlaid with bold red-orange to reddish-brown blocks and bars that form an almost checkerboard or maze-like mosaic, varying enough between individuals that no two look quite alike, capped by a notably elevated third dorsal spine trailing a banner-like flap and eyes that often flash green iridescence. Like a hawkfish, it doesn't swim actively but props itself on oversized pectoral fins atop ledges, rubble, and coral branches, watching the water below and dropping onto small prey with surprising speed. In the wild it lives on deep coastal drop-offs and rubble zones, which explains its preference for shaded ledges and dimmer corners of the display. It's reef safe and won't harm corals, clams, or sessile inverts, and it generally leaves the cleanup crew alone, though it may take a very small hermit or shrimp if the chance arises. It's peaceful and rather shy, mixing well with clownfish, cardinalfish, anthias, firefish, fairy wrasses, and other calm reef fish, but it may act territorial toward similarly shaped bottom dwellers like small gobies, blennies, and dartfish that compete for the same perches. Avoid housing it with anything large enough to eat it, like groupers or lionfish, and steer clear of boisterous species that could intimidate it into hiding at feeding time.

Aquarium Requirements
This is a genuinely excellent nano candidate, comfortable in a 20 gallon tank and thriving in 30 to 40 gallons, and honestly the smaller displays make a fish this cryptic easier to appreciate. Aquascaping is what matters most: provide abundant live rock with ledges, overhangs, rubble pockets, and shaded caves so it has both a perch and an immediate retreat, since a sparse layout will leave it stressed and rarely seen. Subdued to moderate lighting suits its deep-water origins, and low to moderate flow with calm zones near the perch works best. Substrate is optional and can be chosen purely for looks. A tight-fitting lid with screened overflows is recommended, as these small fish can slip through openings. The one thing to stay on top of is feeding, since a shy specimen may hang back at mealtime, so target-feed small portions toward the perch, and many keepers have good luck feeding with the room lights off or releasing live gut-loaded brine so food lingers in the water after they step away. Once acclimated, it's a hardy, bold eater that often trains onto pellets.

Specifications
Approximate Size: 0.75–1.5"
Diet: Carnivore; frozen mysis, vitamin-enriched brine shrimp, calanus, copepods, and finely chopped shrimp, mussel, or fish flesh, with quality small carnivore pellets accepted once settled, fed 1–2 small meals daily
Origin: Indo-West Pacific
Care Level: Easy to moderate
Reef Safe: Yes
Temperament: Peaceful and shy
Minimum Tank Size: 20 gallons
Special Considerations: Reef safe and peaceful, but shy enough that it needs plenty of ledges and shaded retreats plus targeted feeding to make sure it gets its share.