The genus Brachygobius is a nexus of species in the true goby clade, that are collectively known as bumblebee fishes or bumblebee gobies, in account of their colours and patterning. Often they are seen in dealers aquariums, because they are petite and beautifully colored. Yet much confusion exists as to which exact species is being traded, and what water conditions they might benefit most from, or are natural to the wild gobies. Particularly, the question of proper salinity, with confusion and dubious, repeated 'facts' as to their wild habitats.
B. doriae, B. nunus, and B. xanthozonus in particular, are often confused, and indeed, there is confusion even among ichthyologists, as to which of the Brachygobius species an individual bumblebee fish, or Its population, might belong to. The species of Brachygobius are, in nature, partially separated by environmental niche partitioning, with some species present in wild freshwaters. However, the Brachygobius sp. most usually encountered in the aquarium trade, are in fact from brackish waters.
For instance, B. doriae is sympathetic with Rhizophora mangroves, as well as fish like mudskippers, siganids, and archerfishes, in the muddy lower (and thus tidal) reaches of tropical Asian rivers. Thus this species, chosen as an example, would appreciate a quite higher brackish salinity, than books might suggest. But also, it's presence overlaps with that of the palm, Nypa, which is not as salt tolerant as is Rhizophora, so it would be wrong to reckon B. course as a marine fish.
Smaller Brachygobius species, such as B nunus, might grow to around 1 inch or 2.5 centimetres long. Larger congeneric species of bumblebee fishes, can grow to about 4 centimeters, or over 1 and a 1/2 inches. The small size of these beauties has often appealed to those seeking oddballs or brackish fishes, but finding themself with limited space. Although the male gobies can be territorial to one another, its possible and imperative to house members of these species, in a group of about six or more fishes. Single fishes are too easily stressed, it seems. A combination of factors makes these fish unsuitable for a typical community tank, although with careful thought, they can share with other benign brackish fishes.
Its also worth noting that these gobies appreciate it demand warm end tropical temperatures, higher than the 24 degrees centigrade standard, that is probably the norm for tropical tanks. Perhaps a temperature between 25 and 28 degrees centigrade would be ideal for their aquarium. The wild gobies show a positive association, with a muddy substrate. Again contrary to information in books, these gobies do not need crystal clear water, as they evolved in conditions of turbidity. Their presence in mangrove habitat, means that non-toxic leaf litter and wood, are suitable choices for the aquascape also. Wood could be arranged to imitate the appearance of mangrove roots.
Brachygobius sp. aren't quite as finnicky about eating, as some aquarium literature might lead you to believe. These gobies will, at least if acclimatised, take to defrosted foods, and do not require regular feedings, of love invertebrate prey. Some of them even adjust to nipping proprietary flake foods, although it must be cautioned, most of them will not accept manufactured substitute diets. Given that misinformation about feeding this genus, has daunted many aquarists from attempting bumblebee fishes in the aquarium, it isn't really a basis for most fishkeepers to fret unduly about. Misunderstood fishes that are not eating, are presumably stressed in some way.
