Annie's Dwarf Goby or Halmahera Goby (Stiphodon annieae), family Oxudercidae, order Gobiiformes, endemic to streams with rocky bottoms in Halmahera, Indonesia

One of the more distinctive species of Stiphodon in the hobby, is the cobalt blue or opal cling goby, S. semoni. In the freshwater tropical trade, this species can also be known as the neon goby, but it must not be confused with the Atlantic goby species of that name, which is well loved by 'reefers'. The cobalt blue goby is quite a small aquarium fish and it grows to only 5 centimeters long, or 2 inches. Despite its distinctiveness, it is still sometimes mistreated as S. elegans, which is actually of the same approximate length. (Online I have seen the name of S. elegans most commonly associated with a 'green riffle goby'; but as a non-specialist, I can only express doubt that such identifications are accurate. If ichthyologists cannot sort Stiphodon systematics, then aquarium retailers may hardly be expected to do better!)

The natural range of S. semoni is throughout the Indo-Malayan archipelago, and onto the Solomon archipelago and Queensland. Such a broad distribution is possible because stiphodonts are not freshwater fishes throughout their whole life cycle: they initially drift out to sea, and there join the zooplankton as larvae, before returning to freshwaters when they enter their juvenile stage. Supposed S. semoni from the Philippines and perhaps other more northern localities, are nowadays regarded as a distinct species, named S. atropurpureus, also called a cobalt blue goby and also growing to the same adult length as S. semoni. Both these species appear to be found in the aquarium trade.

Online resources aimed at aquarists tend to be strangely vague, when they are specifying how to care for stiphodont gobies. However the ecological data I am aware of, reveals both S. semoni and a sympatric S. cf. elegans to inhabit streams with a temperature of 23 to 25 degrees centigrade, and a pH slightly above 7, yet below 7.5. Although websites say that these gobies live in water as warm as 28 degrees, I haven't seen any data that corroborates this, which is maybe because running water has a cooling effect. Where stiphodonts compete with other fishes they tend to be one associated with the upper reaches of streams; otherwise they are more broadly found throughout their entire streams, including the more sheltered pools that form. It might thus be seen that they are not strict microhabitats specialists as some sources claim, although they are associated with good quality, flowing freshwaters. As these are specialized fishes that graze biofilms upon rock, they should be kept in well illuminated tanks that have an aqua scope of cobbles and larger rockwork: the bright light will encourage the algal biofilms on which these gobies subsist. These are essential for these fishes to survive in the wild, although their natural habitats also feature sand. Their aquarium water must be clear, well oxygenated, and generally of a high quality; the water movement should be greater than that which is usually in a tropical community tank, yet it need not be forceful.

I once bought fish, named emerald river gobies, Stiphodon elegans. The species was presumably misidentified, because those seen (rarely) in the freshwater aquarium trade, are S. semani, misidentified as S. elegans. Their usual trade name, is cobalt river goby, or blue neon goby. Though the genus Stiphodon, is not to be confused, with the marine neon gobies of the genus Elactinus, that are more common in aquaria. Their habitat, captive care, form, and function, are all dissimilar. On the other hand, a trade name might conflate more than one of the species included in Stiphodon.

S. semani is native to clear, coastal, moderately to swift flowing streams, with rocky and boulder strewn bottoms. This environment favors the growth of natural biofilms, which form the diet of these gobies. The reason these gobies live in coastal streams, is because their larvae are dispersed as plankton, by the neighbouring sea. However, the adults of this species, are entirely freshwater denizens. They deposit their eggs in the freshwater streams, for them to hatch, and the larvae to migrate downstream, as freshwater plankton.

No salt should be added to the aquarium water, if the adult S. semani are to be kept. These gobies require a biotope tank, but are not considered difficult to maintain, if their captive needs are respected. These fish are peaceful bottom dwellers, but any tankmates will need to share their specialised demands. Fortunately, they should be maintained in a suitably large social group. Nor does the aquarium need to be large, for these 4.6 centimeter, or 1.8 inch long fish. What they need is rocks, and oxygenated water with a good flow.

The pH that is best for them, is probably slightly acidic to neutral (6.5-7?) though I haven't seen data from collection localities, and I am inferring from other Stiphodon sp. and their habitat preferences. Because S. semani inhabits sunny, lowland areas in the wild, the temperture can be maintained at 24 to 28 degrees. Although the gobies are not violent, the males are competitive, so the decor should be places to break their lines of sight. A further consideration should be, that these gobies are good jumpers, and can also climb the glass, out of the water. Therefore, the lid must be escapeproofed, knowing that Stiphodon is slightly amphibious.

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