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.
For a zooplanktivore such as Anthias, who are frequent feeders, withholding food isn’t necessarily advantageousQuestionI’ve been told that it’s a good idea to avoid feeding aquarium fish on occasion, for example once every week or once every other week. I guess this stands to reason because fish in nature can’t always get a meal. Do you agree with this, and if so, how frequently do you recommend doing it?” – Submitted by Candace Brown Answer While I don’t have an issue with the practice of occasionally fasting fish, I’m always wary of making any sort of blanket recommendation such as “Marine fish should be fasted every X number of days.” In my opinion, a much better approach is to think in terms of feeding in a manner appropriate to the particular species—which may or may not include fasting. For instance, some predatory species, such as groupers and moray eels, naturally take in large prey items in one sitting and then go without eating for a relatively long interval until another prey item happens along. With these fish, it may be appropriate to feed only once or a few times per week and then allow them to fast in between meals. On the other hand, zooplanktivores and herbivores (such as anthias and many of the tangs/surgeonfishes respectively) naturally feed frequently, if not continuously, throughout the day. Thus, in an aquarium setting, it’s appropriate to provide multiple small feedings each day for zooplanktivores and continuous grazing opportunities for herbivores.
While a fish might seem to have an exclusive diet, they’ll often chow down on “off-menu” offerings, as wellCarnivorous fish eat meat, herbivorous fish eat algae/plants, and omnivorous fish eat both. That’s the order of things, and any fish we buy for our aquariums should fit nicely into one of these categories so we know exactly what to feed it, right? Well, if that’s the case, why on earth do my blue-chin triggers (Xanthichthys auromarginatus)—carnivores by nature—always beat my tangs and foxface to the dried algae sheets I offer and actually eat the lion’s share? After all, FishBase describes X. auromarginatus as “[forming] loose aggregations a few meters above the bottom where it feeds on zooplankton, particularly copepods.” Nowhere in this statement do you see, “Oh yeah, and it likes to tear into algae from time to time, too!”On the flipside of the coin, just as my triggers seem to enjoy ordering “off-menu,” my herbivorous yellow tang (Zebrasoma flavescens), Atlantic blue tang (Acanthurus coeruleus), and one-spot foxface (Siganus unimaculatus) will greedily gobble up any meaty items that they can fit in their mouths as well. What gives?
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.