Members of the genus Parapercis can be found in stores as dragonets, gobies, blennies and even “sand hoppers” (a term usually reserved for a group of beach-dwelling crustaceans). They certainly do seem to occupy a similar niche as the first three groups of bottom-dwelling fish, which spend their time on the sea floor, propping themselves up on their pelvic fins. They also have a pointed snout like a dragonet and a long dorsal fin like certain blennies. To make matters more confusing, if you look this genus up in field guides, these fishes may be referred to as grubfish, weevers or whitings. But what are they really, how do they behave, and what is required to keep them healthy in a home aquarium
It turns out that the Parapercis, along with three other genera, belong to the family Pinguipedidae and are known to most ichthyophiles as sandperches. These fishes are also durable, engaging aquarium pets. We’ll examine the biology and husbandry requirements of these often misidentified and overlooked reef dwellers.
Classification and Biology
Sandperches are frequently found resting on rubble bottoms, but they also live on sand, mud, gravel, coral rock and live stony coral substrates. Most of the species found in the aquarium trade are common in relatively shallow water, but there are some that occur to depths as great as 765 feet. Although many Parapercis are found on or near coral reefs, a number of species inhabit rocky reefs in warm, temperate seas.
Most Parapercis use their pelvic fins to prop the front part of their bodies up above the substrate. These fishes will move from one spot to another by hopping along on their pelvic fins, or will use their tail fin if they need to travel at greater speed or over a longer distance. When threatened, they hide under rocks or sometimes duck into burrows excavated by other marine organisms.
Sandperches feed off of or near the bottom, and they usually pounce on invertebrates and small fish. When they feed, they lower their head to inspect the substrate. If a prey organism is detected, they shoot forward to ingest it. A study carried out on the speckled sandperch (P. hexophthalma) demonstrated that in a 15-minute period of time, females take an average of 10 bites at the substrate, while males take only three. This discrepancy in feeding rates occurs because male sandperches spend much of their time patrolling their territories, looking for intruders (of their own species). There are also several species that feed on zooplankton in the water column. There is evidence to suggest that at least some species of Parapercis feed more on crustaceans when small, adding more fish in their diet as they grow larger.
Sandperches are the ultimate opportunists. They regularly follow other fish species (e.g., stingrays, goatfish) that disturb the substrate when they feed, in order to pounce on prey items flushed by their foraging “partner.” This habit can be used to the advantage of an underwater photographer. You simply have to flip bits of rubble or stir the sand with your hand, and a nearby sandperch will usually move in to seek out feeding opportunities. If you keep a sandperch in an aquarium with substrate-stirrers, they will often exhibit this feeding association in captivity, as well.
Sandperches are protogynous hermaphrodites: They are all born female, and females turn into males as needed. Male and female sandperches often differ in color and size. Males tend to be larger and often more boldly marked. All the species studied thus far change sex from female to male. The majority of sandperches are also territorial, with the male defending an area that contains one to five females. In turn, females occupy territories — from which they exclude each other — within the male’s larger domain.
A male sandperch’s territory may cover an area from 185 to more than 3,000 square feet — all much larger than even the most immense home aquarium. Males typically avoid one another, but on occasion, they will meet along their territory boundaries. This often elicits some interesting communicative behaviors. One of these is a display in which the two rivals bob up and down on their pelvic fins (like the “push-ups” exhibited by some lizards), erecting their median fins and spreading their gill covers. If a male should enter another male’s domain, the resident fish may charge, bite and chase the intruding fish.
In contrast to many others in the genus, the redspotted sandperch (P. schauinslandi) forms aggregations, which is the most common social unit in zooplankton-feeding fish. The blackfin sandperch (P. snyderi) is also unique, in that it lives in overlapping home ranges. Like others in the genus, this species is haremic but differs from those Parapercis studied to date, in that males regularly engage in “sneaking” behavior. That is, a male will dash in and attempt to join a spawning pair and release its gametes at the same time as the initiating male.
The Sandperch Tank
Sandperches are durable aquarium inhabitants. Adults of the smaller species (e.g., redspotted sandperch) can even be housed in tanks as small as 30 gallons.
Whenever you keep a marine fish, you should attempt to recreate the microhabitats where it normally dwells. In the case of the sandperches, this means dedicating a good portion of the aquarium bottom to sand and/or rubble — the percentage of bottom dedicated to this substrate type being a function of the tank size. For a 55-gallon tank, for example, it should be 50 percent of the tank bottom, and for 75 gallons, devote 30 percent of the tank bottom to sand and/or rubble.
A substrate composed at least in part by sand is a good choice because it will provide some natural fare for your sandperch to feed on if the tank’s infaunal (sandbed-dwelling) community is allowed to mature before adding the sandperch (or other predators of infaunal organisms). That said, in a smaller tank, it probably will not take a sandperch long to pick off the sand-dwelling prey items that live near the substrate surface. These fish do not dig for food, but as mentioned above, rely on the digging activities of others to access buried prey.
In the wild, some sandperches will dart away from a potential predator, or they might dash into a interstice in the rubble-strewn bottom. In the aquarium, dashing will not get them far and may result in their catapulting themselves out of an open tank. To ensure your sandperch does not go carpet surfing, make sure there are several good places for the fish to hide on the aquarium bottom, and keep the top covered. These fish are also likely to leap from an open tank when being harassed by a tankmate or if all the tank lights are suddenly extinguished. A small nightlight can also help prevent nocturnal jumping events.
Sandperches can be kept in reef aquariums — but select the species you keep carefully. Larger sandperches will make short work of ornamental crustaceans (e.g., anemone crabs, cleaner shrimp, anemone shrimp, pistol shrimp, small boxer shrimp), worms (including feather dusters), and smaller serpent/brittle stars. They may even eat smaller fish. If a prey item is too large to swallow whole but small enough to be subdued, they will grasp the quarry in their jaws and bash it against a piece of rubble until the prey breaks into bite-sized morsels.
That said, they can also earn their keep by consuming undesirable live rock freeloaders, including small mantis shrimp and hairy xanthid crabs. Unlike some other bottom-dwelling carnivores (i.e., frogfish and scorpionfish), sandperches are less likely to sit on corals and irritate them.
The best reef tank sandperches are the redbarred (P. multiplicata), redspotted (P. schauinslandi) and Snyder’s (P. snyderi). All three are smaller, attaining a length of around 5 inches. Their smaller size means they are less of a threat to their tankmates and don’t need as much rubble/sand bottom to behave naturally.
The larger Parapercis species should be housed in a fish community with moderately aggressive or larger, less aggressive fish species. For example, they can be kept with squirrelfish, soldierfish, comets, snappers, tilefish, angelfish, butterflyfish, rabbitfish, surgeonfish and certain triggerfish (e.g. redtooth trigger, Odonus niger).
Although sandperches are rarely aggressive toward unrelated species in the wild, they can be aggressive toward other bottom-dwelling predators in an aquarium, especially those with a similar body plan. This includes lizardfish, flying gurnards, small flatheads, jawfish, small hawkfish, sand divers, worm gobies, sleeper gobies and tobies. Do not house sandperches with extremely passive species, such as seahorses and pipefish, ghost pipefish, shrimpfish, dartfish, firefish, more diminutive shrimpgobies and dragonets. In the wild, larger individuals of some species feed heavily on fish, so avoid keeping them with any fish they can swallow whole.
The long, slender body of a sandperch makes it more susceptible to being consumed by certain predators, such as frogfish, scorpionfish, groupers and soapfish. If you are going to house a Parapercis with any of these carnivores, make sure it’s at least twice as long as the potential predator and that the sandperch is introduced to the tank first. Do not keep them with morays, unless the eel is less than half the diameter of the sandperch. Sandperches may possibly be picked on by lizardfish (if they are introduced to the tank before the sandperch), large hawkfish, larger damselfish and more aggressive triggerfish.
Aggression between sandperches often occurs in the wild when males encounter one another along territorial boundaries. To avoid such interactions in captivity, it is best to house only one sandperch per tank. If the tank is large enough (180 gallons or larger), you may be able to keep a male and female sandperch in the same tank; but never place two individuals of the same sex together.
If you place a male and female in the same aquarium, add them simultaneously, and watch them carefully to make sure the male does not injure the female. Another possible way to acquire a pair is to purchase two juveniles or two females of a Parapercis species. It is likely that one individual may change into a male. That said, there are no details as to whether sex change is socially controlled.
Aggression is also likely to occur between sandperches of different species, especially in smaller aquariums. Field studies have demonstrated that some sandperches are more aggressive than others and that the territories of different sandperch species rarely if ever overlap. For example, in southern Japan, the speckled sandperch (P. hexophthalma) is more belligerent than the latticed sandperch (P. clathrata). When the latticed sandperch enters the territory of the speckled sandperch, it is aggressively driven from the area. In contrast, when a speckled sandperch invades the territory of a latticed sandperch, the latter species usually fails in its attempts to drive off the more aggressive intruder.
I have had some success keeping two species of juvenile sandperch together in medium-sized and larger aquariums when both specimens were introduced simultaneously.
Food and Health
Sandperches will eat a wide variety of aquarium fare, including flake food, frozen prepared foods, fresh (chopped) sea foods and live foods, such as feeder fish, blackworms and brine shrimp. Although most species usually feed off the bottom, they will learn to swim up into the water column to take the food floating at the surface or as it sinks. They should be fed at least once a day.
Sandperches are relatively disease-resistant, but like any fish, they should be quarantined for at least three weeks before they are introduced to the display tank. If they come down with a parasitic infection, they can be treated with copper-based medications and formalin. A freshwater dip can also be administered to rid them of certain external protozoa.
That ends our examination of the often misidentified Parapercis. Although sandperches may not be for everyone, most make wonderful aquarium inhabitants in a larger aquarium that is home to a moderately aggressive fish community. There are even a few species that are well-suited to more peaceful aquarium conditions and smaller tanks. Happy fishwatching!
Scott W. Michael is the author of Reef Sharks and Rays of the World, Reef Fishes: A Guide to Their Identification, Behavior and Captive Care; and more. His photos have appeared in publications around the world.