Freckled hawkfish (Paracirrhites forsteri)When it comes to keeping hawkfishes in aquaria, one of the more common admonitions is to avoid housing these predators with fish or crustaceans small enough to swallow. For most of the hawkfish species that grace our tanks, which generally have a maximum size somewhere between 3 and 5 inches, only very small tankmates are truly at risk. A noteworthy exception is the freckled hawkfish (Paracirrhites forsteri), which can reach a rather prodigious size and has a mouth to match. You really have to take that warning seriously with this species! That said, P. forsteri is a hardy, easy-to-care-for hawk that makes a worthy aquarium candidate provided tankmates and housing are chosen judiciously.Physical traits P. forsteri has the deep, stout body and high-set eyes, typical of the hawkfishes. Its maximum size is approximately 8½ inches.
Raccoon Butterflyfish (Chaetodon lunula)Some of the marine fish we like to keep are surprisingly recognizable to both hobbyists and non-hobbyists alike—probably because they’re frequently depicted in photographs and artwork. Among these iconic fishes is the raccoon butterflyfish (Chaetodon lunula) of the Indo-Pacific and southeast Atlantic, a very hardy species that’s better than your average butterfly in terms of aquarium suitability and even beginner-friendliness. C. lunula would also be a great choice for natural pest-anemone control in reef tanks if it could be kept in such a system safely (but, alas, it cannot—more on this later). Physical traitsC. lunula has “typical” butterflyfish morphology, with a highly laterally compressed body and a pointed snout. Its color is orangish-yellow overall with a dusky hue on the dorsal half of the body and faint diagonal stripes on the ventral half. Like its terrestrial namesake, its eyes are obscured by a black “mask.” Behind the mask is a white bar, and two dark bands edged in yellow extend upward from the white bar.
Yellow watchman goby (Cryptocentrus cinctus)Marine aquarium hobbyists who maintain nano tanks, whether by choice or necessity, often find it challenging to acquire fish that are well suited to their diminutive systems. But in the yellow watchman goby (Cryptocentrus cinctus), they can get all the attributes they seek—small mature size, attractive coloration, hardiness, and interesting behavior—in a single package. While the yellow watchman goby, aka the yellow shrimp goby or yellow prawn goby, can be housed by itself with no problems, in my opinion, it’s much more interesting and rewarding to keep it as it commonly occurs in nature—with an Alpheus spp. pistol shrimp (e.g., Alpheus bellulus, the tiger pistol shrimp) sharing its burrow.In this mutualistic symbiotic relationship, the shrimp, which has very poor eyesight, continuously excavates the burrow while the goby stands sentinel against predators. Almost at all times, the shrimp keeps at least one of its antennae in contact with the goby so it can immediately sense when danger is near via the goby’s body language. Physical traits C. cinctus has a torpedo-like body shape; two distinct dorsal fins; a rounded caudal fin; the typically goby-esque fused pelvic fins; high-set, bulbous eyes; and an oversized, “frowning” mouth.