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Gobies
Like the rabbits in Richard Adams’ novel Watership Down, while the goby may have a thousand enemies, so long as he is alert and full of tricks his people will never fail. For while these small, unassuming fish may not seem much they absolutely dominate the brackish water environment. They are perhaps the definitive brackish water fishes, occurring wherever the sea reaches the shore or blends into rivers, streams and swamps, and you are as likely to see gobies in a cold North Atlantic sea loch as a tropical lagoon in northern Australia. At least a thousand different species have been described, undoubtedly there exist many more. Most live on the bottom, usually in burrows. In some cases the burrow is shared with varieties of shrimps or worms that excavate the burrow while the goby keeps lookout. Other gobies are cleaners, with flamboyant colouration to advertise their services. Still others can crawl out on land to feed on mudflats. All are characterised by fused ventral fins which form a sucker. It is believed that the ancestors of the gobies lived in mountain streams, where this served to stop them getting washed away, and only later did they return to the estuaries and coastal marine environment they are now supremely successful in.
Bumblebee gobies, Brachygobius spp.
Note: Thanks to Naomi Delventhal for her help with these problematical fishes. She has provided a useful summary of bumblebee goby needs and breeding here.
Note: Bumblebees are often ignored by larger fish, perhaps because of their wasp-like colours, but some larger fish will eat them, including knight gobies. Choose tankmates with care. Thanks to CFC for this.
The Asian bumblebee gobies Brachygobius are probably the most widely seen non-marine gobies in aquarium stores. In the wild some species inhabit both fresh and brackish water while others are exclusively found in freshwater, but in captivity all seem to do well in slightly brackish water. They can also be kept in completely fresh water provided the water is not too soft and acidic. Although a pH of at least 6.5 is necessary, this still means they can be combined with neons, cardinals, dwarf plecs, Corydoras, and so on. Bumblebee gobies will also adapt to brackish water very readily, a specific gravity of around 1.005 being adequate for keeping these fish alongside brackish water species such as pipefish and mollies.
Unfortunately, many people are not successful at keeping these fish alive for long. Three rules need to observed. Firstly, do not expect them to take flake foods, they won’t. Some frozen foods (such as lobster eggs) are taken, as are live foods such as Daphnia and bloodworms. Secondly, they cannot compete with very active fish at feeding time. In large tanks, they may be successful at finding bits of food the other fish have missed, but in most community tanks these gobies can easily starve to death. Finally, bumblebees need good filtration and plenty of oxygen. They will not last long in tanks that are overstocked or inadequately filtered.
The best sort of aquarium for bumblebee gobies is thickly planted, though whether you use live plants or plastic is up to you. Useful plants include Java Fern, giant hygrophila Nomaphila corymbosa, and onion plants Crinum thaianum. Allow these plants to form a thick tangle, which will help the gobies to feel comfortable. Driftwood and blackwater extract can be used (provided the filter is buffered to prevent the pH becoming too acidic), and this will lend the water the peaty, dark quality characteristic of their swampy habitat. Decorate the bottom with large snail shells, such as those of apple snails.
To spawn these fishes they must be provide with some sort of cave or burrow (a small flower pot is ideal). The fish form pairs, and are markedly territorial. During the breeding phase, the males become much paler in colour, the black bands weakening considerably and may vanish altogether. The female is very round when filled with eggs. The addition of cooler, fresh water often triggers spawning. The female lays the eggs inside the cave and then leaves the male to guard the eggs and raise the brood. The fry swim in the open water at first and will need tiny live food (infusoria) at first, graduating on to newly hatched brine shrimps. After a few days the fry settle down onto the bottom and swim rather less.
There are a number of species of bumblebee goby, found in fresh and brackish water conditions, some of which are imported very regularly, primarily Brachygobius doriae, but also Brachygobius sabanus and Brachygobios nunus. Identifying these fishes without being able to place them under a microscope is notoriously difficult. Up to ten will do well in an aquarium as small as 20 litres (5.5 gallons), and the larger the group, the less aggression between individuals tends to be.
Many aquarium books will refer to Hypogymnogobius xanthozona, a very rare species that is not commercially collected or traded (there are in fact very few specimens even in museum collections). Where this name is used in the aquarium literature, it is safe to assume that one of the Brachygobius species is actually being referred to.
Violet gobies, Gobioides and Odontamblyopus spp.
Quite widely sold in the USA is the violet goby Gobioides broussonnetii, a large eel-like goby on the Atlantic coast from South Carolina through to northern Brazil. In Europe other species are more often seen, including Gobioides peruanus from South America and Odontamblyopus rubicundus from Southern Asia. True Gobioides broussonnettii have small, mudskipper-like eyes at the top of the head and a series of dark vertical bands running along the flanks. Gobioides peruanus has much fainter bands and they are only really obvious close to the head. Odontamblyopus spp. have virtually no banding and have tiny small eyes set further down the head. The pectoral fins also have hair-like extensions that are used while feeding.
All these fish need a soft substrate to burrow into as well as a large tank proportionate to their size. They are territorial, but they do not seem to do any harm provided each fish has someplace to hide. PVC tubes are inexpensive and widely used for this, but otherwise ordinary aquarium ornaments, bogwood, rockwork, or plants will do fine. They are bottom feeders and sift the substrate to capture small animals such as shrimps and worms. Frozen equivalents work well, along with catfish pellets. They do eat some algae as well, scraping it off with their small but sharp teeth.
While violet gobies are naturally found in freshwater, brackish and marine environments, brackish water with a specific gravity of at least 1.005, and preferably 1.010, is necessary for long term health in the aquarium. Otherwise, these fish are not difficult to keep and they are usually considered to be quite hardy animals.
Knight goby, Stigmatogobius sadanundio
An Asian goby often seen is the knight goby, Stigmatogobius sadanundio. This is found throughout South East Asia. Although it only needs little salt (specific gravity of 1.001 to 1.005 is fine), it cannot adapt to completely fresh water. Of moderate size, 8 cm (3.5 inches) it is peaceful and can be combined with fishes that stay in the middle and upper part of the tank. May take flake, but crustacea, worms and chopped mollusc meat should be a regular part of the diet. Also relishes green leafy algae, which may be substituted with blanched lettuce tied to a weight such as a pebble.
White-cheeked goby, Rhinogobius duospilus
An Asian goby often seen is the knight goby, Rhinogobius duospilus, commonly sold as Rhinogobius wui, is a hardy subtropical species that does well in small aquaria. It does well in freshwater and brackish water conditions (SG around 1.005) and gets on well with bumblebee gobies, knight gobies, and other small, peaceful species. Because it is a subtropical species it does not appreciate temperatures above 24° C (75° F) for extended periods. If you must keep it in a tropical aquarium, ensure that the tank is not overcrowded and use plenty of aeration to keep the dissolved oxygen concentration high. It is a lively species that readily eats bloodworms, crustacean eggs, small pieces of shrimp, and Artemia. It will not eat flake.
Freshwater gobies, Awaous spp.
Note: Thanks to Bruce Hansen and Naomi Delventhal for the information on these gobies. Naomi has written a detailed article on the care and breeding of these fishes for Gobiidae.com
The freshwater gobies of the genus Awaous appear from time to time and can be good aquarium fish. There are various species, Awaous flavus from the tropical South American coastline being the most commonly imported. It inhabits brackish and fresh waters and requires slightly acidic to slightly alkaline, moderately hard water to do well. In Europe, the scribbled or pearl goby Awaous grammepomus from South East Asia and New Guinea is more frequently seen, though it requires much the same conditions. An Australian species, the Roman nose goby, Awaous acritosus, also does well in freshwater aquaria.
These are medium sized gobies, typically 8 to 15 cm (3 to 6 inches) in length, and so need a fairly large aquarium. These gobies are inveterate burrowers, and a soft, sandy substrate is absolutely essential. Like spiny eels and flounders they will bury themselves completely if they can, especially if they feel threatened. Awaous feed in the same way as the eartheater cichlids, staying close to the bottom and sifting mouthfuls of sand for insect larvae, worms, and other small invertebrates. In captivity they will happily take frozen foods and small prawns as well as various live foods; they also need some plant material, either soft algae or a substitute such as blanched lettuce leaves or defrosted frozen peas.
Awaous gobies are widely distributed and found in both the Old and New World, and as adults at least are tolerant of a wide range of salinities, although in most cases they are found in fresh or only slightly brackish water. Reproduction is different to most of the commonly kept gobies in that while spawning does take place in freshwater, with the male guarding the eggs inside a small cave, after hatching the larvae drift downstream to the sea, where they pass through a planktonic stage. There they feed and grow, and if they are fortunate the ocean currents will bring them to some body of brackish water such as a river estuary or mangrove where they will metamorphose into their juvenile form. These little gobies will then swim upstream into their coastal streams they favour. Undoubtedly this planktonic stage accounts for the very wide distribution of these fish, allowing successive generations to hop from island to island or along the coastlines of continents much more successfully than the adult gobies could under their own steam. But it also makes them difficult to raise in captivity because the fry will not accept the usual foods supplied to young fish by aquarists.