Aquarium Fish: Gobies of the Genus Amblygobius

The genus Amblygobius is
comprised of 14 species that are distributed in the Indo-Pacific.
Two of these gobies are encountered in the aquarium trade with a
great degree of regularity, while at least four others show-up
occasionally. Unlike many gobies, the Amblygobius spp.
spend most of their time hovering in the water column, not in
repose on the substrate. Most species are also omnivorous,
feeding on algae as well as tiny invertebrates. There are some
that acquire these invertebrates by taking in mouthfuls of
substrate and sifting it through their gill rakers. Rather than
examining the husbandry of the genus as a whole, I think it would
be more valuable to look at the two most common aquarium species
in detail.

Rainford’s Goby (Amblygobius rainfordi)

Rainford’s goby is greenish brown overall with orange
lines and has become a staple in the marine fish trade since
about 1990. Its availability in the hobby corresponds with the
increased popularity of reef aquariums. Although this fish will
not harm sessile invertebrates, and is thus a suitable addition
to the reef aquarium, it really does best if kept in a tank with
filamentous algae (something most reef aquarists abhor). If the
tank does not support an algal crop, it will often become
emaciated. If the aquarist is persistent, it is possible to get
these fish to accept introduced fare, like vitamin-enriched live
and frozen brine shrimp, mysid shrimp, and prepared foods for
herbivores. But, as I keep more A. rainfordi I have come
to the conclusion that green and/or red filamentous algae is
almost essential to keep most individuals.

Amblygobius01.jpg

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Rainford’s goby is a colorful
addition to the reef aquarium, but will do best if some
filamentous algae is present in the aquarium.

With the exception of closely related species, A.
rainfordi
is rarely aggressively toward fish tankmates. I
have kept it with other Amblygobius spp. with varying
degrees of success. If housed with larger forms, it is likely to
be picked on if the tank is small. It may fight with the
similarly-shaped Hector’s goby (Amblygobius
hectori
).

Juvenile Rainford’s gobies can be kept together in
medium-sized tank if introduced together, but adults often
quarrel. Therefore, it is best to keep one per tank. Just because
you purchase a “mated pair” of A. rainfordi,
it does not mean that they will get along. For example, I
acquired a supposed mated pair of Rainford’s gobies that were
happy together when initially introduced, but after several days
one of the animals disappeared. This individual reappeared after
about four days, only to be picked on incessantly by its supposed
“mate.” The more dominant fish displayed at, chase and
darted at and rammed the slightly smaller conspecific every time
they came into close proximity to one another. The subordinate
rarely sifted the substrate while the more aggressive fish, fed
more frequently. The subordinate fish lost weight, began
exhibiting a curved back, sunken dorsal musculature (a sign of
malnutrition) and finally perished. I should point out, that in
the wild, this fish usually occurs singly, not in pairs.

Amblygobius02.jpg

The nocturn goby is likely to dig
holes and burrow under rock work. It is less common in the hobby
than some of its congeners.

Rainford’s goby should be kept with peaceful species.
Avoid housing it with fishes that are prone to picking on small,
substrate-bound fishes, like dottybacks, hawkfishes and sand
perches. Amblygobius rainfordi attains a maximum length
of 2.6 inches and can be housed in very small tanks. All of the
members of this genus will jump out of open aquariums if they are
harassed by aggressive tankmates or if startled when the lights
are turned off.

Amblygobius03.jpg

The crosshatch goby is a sand
sifter that will take small mouthfuls of substrate and filter it
through its gill rakers. It feeds mainly on small crustaceans and
some algae.

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Amblygobius04.jpg

The crosshatch goby can vary
somewhat in color, depending on its surroundings (e.g., substrate
hue).

The Rainford’s goby is similar to several other species
that occasionally make it into the aquarium trade. These are: the
crosshatch goby (Amblygobius decussatus), Hector’s
goby (A. hectori), and the nocturn goby (A.
nocturnus
). The husbandry of these species is quite similar
to that of A. rainfordi. The nocturn goby is more likely
to dig burrows under rock work, while the crosshatch goby seems
to be less dependent on algae to survive and may also be more
likely to tolerate the presence of conspecifics.

Brownbarred Goby (Amblygobius phalaena)

This is a larger member of the genus, attaining a maximum
length of around 6 inches. It can be employed in a utility role
in the reef aquarium as it will help keep the upper layers of
live sand stirred by taking mouthfuls and then expelling it
through its gills. It is a more vigorous substrate-sifter than
the Rainford’s goby. It spends more time engaged in this
behavior and also, in part because it is larger, penetrates
deeper into the sand bed. However, it is not as likely to disturb
the deeper sections of sand beds like the sleeper gobies
(Valenciennea spp.).

Amblygobius05.jpg

The brownbarred goby is regularly
encountered by aquarists and is a fairly durable aquarium
species.

Amblygobius06.jpg

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The darker color phase of the
brownbarred goby. This species also “appreciates” some
plant material in its diet.

This species tends to be hardier than A. rainfordi.
While a filamentous algae crop will greatly facilitate the
husbandry of the Rainford’s goby, it is less important
element in A. phalaena care (although, the latter does
feed heavily on algae in the wild). It can be fed
vitamin-enriched live and frozen brine shrimp and mysid shrimp,
as well as prepared foods for herbivores. If placed in a tank
without filamentous algae, live sand, or live rock, feed at least
twice a day, but if natural foods are present, you can feed it
less frequently. Keep an eye on its weight to determine if you
should feed more.

Although not usually considered to be a threat to sessile
invertebrates, I had one A. phalaena that would pull
zoanthids off of a rock, chew on them and then spit them out! It
is a predator on flatworms that can become a real pest in a reef
aquarium.

The brownbarred goby is rarely quarrelsome with
heterospecifics, but they will fight with each other. When
quarreling, they will erect their fins, rub their ventral
surfaces together, and ram each other with their open mouths.
Because of their propensity to fight, it is best to keep it
singly — that is, unless you can acquire a male-female pair.
Achterkamp (1991) suggests that males have spots on the tail,
while females lack them, however, more study is required to
confirm this observation. Spawning may occur in captivity
(Achterkamp 1991, Delbeek and Michael 1993). When they are ready
to spawn, the pair will dig a burrow that will serve as their
nest. In most cases spawning occurs at night. The male defends
the dirty-yellow clump of eggs, driving off the female and
chasing potential egg predators from the nest site. The eggs
hatch in about 6 days. Spawning can occur as frequently as
several times a month, but some pairs may spawn much less
frequently than that.

Amblygobius07.jpg

The darker color phase of the
brownbarred goby. This species also “appreciates” some
plant material in its diet.

Do not keep the brownbarred goby with overly aggressive fishes
that stay on or near the substrate. However, if the tank is large
enough, this fish will often be ignored by its tankmates. The
brownbarred goby is very similar to the tailspot goby
(Amblygobius albimaculatus) and Sphynx goby (A.
sphynx
). The captive care requirements of these species are
very similar to that of A. phalaena. These three species
are likely to quarrel with one another if they are kept
together.

I hope this introduction to the more common members of the
genus Amblygobius will help you in selecting a species
that is best for your aquarium venue. Although they have some
special husbandry needs (e.g., filamentous algae), they can
provide the dedicated aquarist with years of enjoyment. Until
next time, happy fish-watching!

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References:

  1. Achterkamp, A. 1991. Bij de voorplaat… Amblygobius
    phalaena
    . Het Zee-Aquarium 41(5):104-105.
  2. Delbeek, J. C. and S. W. Michael. 1993. The substrate
    sifting gobies – fishes that earn their keep. Aquarium Fish
    Magazine
    5 (11):18-30.
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