Mystery Wrasse (Pseudocheilinus ocellatus)Pseudocheilinus ocellatus, the mystery wrasse (aka the tail-spot wrasse, white-barred wrasse, or five-barred wrasse), is somewhat uncommon in the hobby and usually priced accordingly. But if you can get past the sticker shock for such a modest-sized fish, you’ll find this species can be a worthy aquarium candidate. Physical traitsExhibiting the banana-with-fins morphology typical of so many wrasses, this denizen of the western central Pacific reaches around 4 inches in length. Its yellow-rimmed eyes move independently and seem to be constantly appraising the goings on both inside and outside the tank. Base coloration is quite variable, commonly lavender to pinkish/purplish, while the face is yellow with purple/pink lines. The caudal peduncle is yellow and adorned with a prominent ocellus, or eyespot.
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.
A large, aggressive species, such as a queen triggerfish, is sometimes best kept singlyA diverse community of marine fishes presents quite a visual feast, especially when housed in a reef system brimming with colorful corals. However, in some stocking situations, it’s preferable to avoid the “typical” marine community (if there is such a thing) in favor of a single-species or even a single-specimen tank. Ah, but if you limit your livestock to a single species or specimen, won’t that make for a real yawner of a tank? On the contrary, sometimes systems that put the focus exclusively or primarily on a particular species or individual are among the most fascinating to observe.Here are five circumstances that warrant going single-species or single-specimen: 1. The shy, specialized feeder Seahorses, which are slow, awkward swimmers, shy by nature, and very specialized, methodical feeders, come to mind here. In your average community aquarium, these fish would basically be doomed, as they’d be unable to compete with bolder, faster-moving tankmates for food and would be unable to tolerate the brisk water movement typical of such systems. Not to mention, a community tank of any appreciable size would make it extremely difficult to provide the steady supply and high concentration of suitable food items necessary to sustain seahorses. On the other hand, in a small dedicated system with very gentle current, no competition for food, and suitable “hitching posts” to cling to, a group of seahorses can make for a truly mesmerizing display
Threadfin Cardinalfish (Zoramia leptacantha)Walk by an LFS sales tank containing a few specimens of threadfin cardinalfish (Zoramia leptacantha), and you might not give them a second glance. Chromatically speaking, this species isn’t exactly a showstopper compared to some, especially when viewed in your average LFS environment. But don’t let this cardinal’s unassuming appearance fool you; it can make for an impressive display species when kept in groups. Physical traitsZ. leptacantha is a diminutive fish, reaching only about 2.5 inches in total length. It’s laterally compressed and has two dorsal fins, the first fairly elongated relative to the second. As mentioned, this species’ color is nothing to write home about (in case you’re one of those types who like to write home about the colors of fish). It’s semi-transparent to yellowish-silver overall with iridescent blue around the eyes as well as blue and yellow accents on the anterior portion of the body.
Signal goby (Signigobius biocellatus)The signal goby (Signigobius biocellatus), aka the twin-spot, two-spot, or crab-eye goby, is an appealing little sand sifter with fascinating behavior that, unfortunately, often adapts very poorly to aquarium life. Nonetheless, specimens still appear in the aquarium trade, so it’s worth discussing the species here—if only to understand why it’s probably best to pass it by if you should happen to come across one at your LFS. Physical traitsS. biocellatus has a torpedo-like body shape, high-set, bulbous eyes, a comically frowning mouth, and two prominent dorsal fins. In coloration, it’s grayish overall with orange-brown mottling. Each dorsal fin features a large, distinct eyespot, and the pelvic and anal fins are black with blue dots. The maximum size of this goby is around 4 inches. A crabby mimic When you view this fish in profile as it hovers just above the substrate, the twin eyespots create the impression that you’re looking at a crab scuttling sideways along the ocean floor, which might give would-be predators pause.