The photo.....
Classification: Taxonomy, Relation With Other Groups
Squirrelfishes, Family Holocentridae ("Whole-oh-sen-trid-ee") are members of an Order of fishes, Beryciformes ("Bear-eh-see-form-ace"), that is not very familiar to many aquarists.
Some fish taxonomists separate the family Holocentridae into the 'true' Squirrelfishes (Subfamily Holocentrinae) and the Soldierfishes, Subfamily Myripristinae. The Squirrelfish family Holocentridae itself is represented by about sixty five species in eight genera. Most Squirrelfishes are reddish in color mixed with silver and white; all have large eyes, and are nocturnal, hiding in crevices or beneath ledges by day (typically with Cardinalfishes, Bigeyes and Sweepers). These are shallow water fishes, found from the surface to about 100 meters.
Natural Range
Tropical marine, Atlantic, Indian and Pacific reefs.
Habitat
Can you replicate the hiding netherworld of ledges and coves by day, the bottom, food searching, nocturnal swimming space by night?
Size
Most to about six inches in captivity, some to a foot and a half in the wild.
Chemical/Physical
Not demanding; lower temperatures are preferred, 72-78 degrees F.. Higher temperatures may bring on a feeding strike and odd behavior. Higher, steady specific gravity are appreciated, closer to 1.025; maybe due to their close association with invertebrates?
Biology/Other
I'd like to mention that holocentrids produce audible sound, above and below water. They grind their pharyngeal teeth and stretch muscles against their long gas bladders; much like rubbing your fingers along a balloon.
Territoriality
Generally not. Squirrelfishes live comfortably alone as adults. In the wild most live in aggregations as young.
Introduction/Acclimation
Best put in established systems, keeping light on but subdued for a couple of days.
Predator/Prey Relations
Most Squirrelfishes as individuals get along with their own kind, other species of Squirrelfishes and other tankmates. Most would-be predators give them wide berth after looking over their overall spininess.....
Think twice size-wise about using squirrels as reef-tank organisms. They are supreme choices as being hardy and interesting, but will greedily swallow any and all crustaceans that can fit into their expansive mouths. If you lack and do not intend to have shrimp(s) or crab(s), and would like to minimize bristle and other worm activity, consider a squirrelfish.
Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes
They are predators on small very small fishes and mobile invertebrates, principally crustaceans in the wild. Livebearers, shrimp and other fresh and frozen meaty foods are acceptable; avoid pellets, flake and other dry prepared foods; these will not sustain them.....
If your specimens are new, refusing food, or go on a feeding strike, execute a large water change and try a live shrimp with the lights off on the system. Generally Squirrelfishes can be trained to take 'wiggled' krill or other shrimp.
