Brackish Water Fishes
Now for something a lot smaller. Brachygobius (Bumblebee gobies) are suitable for those of you who cannot keep a large brackish water aquarium, because they will be quite happy in a 60 x 30 x 30 cm (24 x 12 x 12 in) tank. Although these fishes are small, we do not recommend using anything smaller than this because it is more difficult to maintain good water conditions in a small body of water.
There are two species available, Brachygobius xanthozona (Bumblebee goby) and Brachygobius nunus (Golden-banded goby), but because they look very similar, both are usually labelled “Bumblebee gobies” in dealers’ tanks. Both are small, 4-4.5 cm in length at most, and both have broad yellow and black vertical bands on the body, but in B. xanthozona these bands are more clearly defined. Both are found in fresh and brackish waters in Asia, but Brachygobius xanthozona has the more restricted range.
Like all gobies, these fishes spend much of their time darting about among rocks and pebbles, or resting on wood or leaves in the mid to lower regions of the aquarium, so design your decor with this in mind. Fine gravel makes a good base for a scattering of pebbles and rocks together with a piece of bogwood. Attach some Java fern to the wood, and plant other salt-tolerant plants in thickets to the rear and sides of the aquarium. If possible provide a cave or two, which can be half flowerpots either left just as they are or camouflaged with stones – the choice is yours, but make sure there are plenty of other hiding places because bumblebees are territorial, so it is important to have sufficient rocks, wood, and so on, so that each fish can stake a claim to its own patch. Then, provided you don’t add more gobies or move the rocks around, there will be no real battles, just the fishes shaping up to each other if one inadvertently enters the territory of another.
Feeding bumblebees can be quite a problem, as only rarely will they accept flake foods. If you are lucky, they will take frozen bloodworm and Daphnia, if not, then you must be prepared to provide live foods of all kinds. They are particularly fond of whiteworm and Tubifex, and will also take most other aquatic invertebrates. If you have limited supplies of these available, it is suggested that you also culture brine shrimps and let these grow on a little before feeding them to your fishes.
Although they will live in hard (above 15° dH) fresh water, they really seem to prefer warm, brackish conditions. Make sure that you have an efficient filtration system as any deterioration in water conditions can cause stress and they may suffer from bacterial or fungal infections. This doesn’t mean that there has to be a torrent of water flowing through the tank – flow rate does not equate with efficiency -just a gentle turnover of the water is fine; the fishes won’t enjoy being washed away.
Breeding Bumblebee Gobies
A water change with fresh water (that is, a reduction in salinity) will often provide the trigger for the fishes to spawn. Males are more colourful than females but at spawning time the females are easy to spot because they are much fuller in the body and, about 48 hours prior to spawning, will show an ovipositor. The pair will spawn either beneath a rock or in a cave, laying up to 200 eggs. At about 28°C (82°F), the eggs will hatch in four days and the male guards the fry. At this time he will defend his brood against all comers, including the female, so she must have a hideaway to retreat to. For the first few days after the fry become free swimming, the shoal moves about the lower levels of the aquarium, but it isn’t long before they, like their parents, adopt a bottomdwelling lifestyle. One of the problems is providing sufficient live foods. It is critical that the timing of brine shrimp hatching coincides with the fry needing it.
Growth is steady provided you can supply enough live foods and plenty of space, so you will probably need to set up another tank in which to grow on the fry. Most losses seem to occur because the fry starve.
Keeping these little gobies in a species aquarium is all very well and good, but it does seem an awful waste of the top layers of the aquarium. A pair of sailfin mollies (Poecilia sp.) make excellent companions for the gobies and in brackish waters they really show their true colours and tend not to suffer from the bacterial or fungal infections that sometimes break out on those kept in fresh water. Being opportunists, they will take the live foods put in for the gobies, but you will soon learn how much will keep both species happy.
A word of warning here: don’t let the aquarium become overpopulated with young mollies or they may overload the filtration and the resulting deterioration in water quality will lead to the demise of your gobies. It will be far better to grow the young mollies on in another tank.