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.
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.
Yasha Shrimp Goby (Stonogobiops yasha)Certain marine fish pack a lot of visual and behavioral interest into a very small package. Such is the case with the yasha shrimp goby (Stonogobiops yasha), also sold under the common names whiteray shrimp goby, orange-striped shrimp goby, clown shrimp goby, and others. This little goby, hailing from the western Pacific, is strikingly colored and patterned, very peaceful, and well-suited to smaller systems. Fairly recently identified, S. yasha is also somewhat uncommon in the hobby and (to my pocketbook anyway) a little on the expensive side, but it’s well worth the price if you can source a specimen. Shrimp symbiontS. yasha is among the various goby species that have a symbiotic relationship with Alpheus spp.
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.