Cobalt Blue Dwarf Goby (Stiphodon semoni)

Males of the Cobalt Dwarf Goby develop deep blue coloration as they mature and compete for the attention of females. This peaceful species is a shrimp-safe fish that is a great addition to the subtropical nano aquarium!

The Cobalt Blue Dwarf Goby (Stiphodon semoni) is a very rare freshwater dwarf goby that is native to Indonesia, Papua New Guinea, and the Solomon Islands. It is known for the deep blue color that male (and, to a lesser degree, some female) specimens display at maturity. Females are not as colorful, but are still very attractively marked with horizontal black and cream-colored stripes.  This fascinating, peaceful fish is an algae and biofilm grazer that is an excellent candidate for the mature nano aquarium.  

An aquarium with heavy water flow (10-15x turnover per hour) and very clean, clear water is required for the Cobalt Blue Dwarf Goby. This fish is native to shallow, clear, fast-flowing waters and it is sensitive to declines in water quality, so regular aquarium maintenance is a must.

The Cobalt Blue Dwarf Goby is a biofilm and algae grazer in nature. It is known to usually accept frozen meaty foods, but such foods should only be fed occasionally. This fish will also sometimes accept high-quality dry foods that are rich in plant matter, but it is absolutely essential that biofilm and algae are naturally available in the aquarium to ensure its long-term health or else it may slowly starve. As long as it is kept in a well-maintained, mature aquarium with good biofilm and algae growth as well as high water flow, the Cobalt Blue Dwarf Goby is a hardy and entertaining fish. It will not bother aquarium plants. In fact, Anubias species are an excellent plant to keep with this goby because Anubias can foster significant biofilm/algae growth in an aquarium with moderate to high lighting.

Most small rasboras, tetras, hillstream loaches, and other small, peaceful fish are good tankmates for the Cobalt Blue Dwarf Goby. Due to its small size and diet, the Cobalt Blue Dwarf Goby can also be kept with dwarf shrimp, although it might eat a few of their fry. Dwarf shrimp are particularly good tankmates in larger aquariums where they can find areas of lower water flow. Peaceful bottom-dwelling fish are also a possibility, but care must be taken to make sure that the passive Cobalt Blue Dwarf Goby is not outcompeted for food. Female gobies will often congregate together, even with other Stiiphodon goby species. Males seem to be able to differentiate between females of different species during courtship behavior.

There are reported cases of the Cobalt Blue Dwarf Goby spawning in the aquarium, but it is very difficult (if not currently impossible) to raise the fry due to their complex larval stages. In nature, adults spawn and their fry hatch in freshwater, then they are immediately swept downstream to marine ocean waters where they feed and develop. As the fry mature, they swim great distances back to full freshwater streams, often on completely different islands than where they originated. At this point, the fry have become young adults are will soon be sexually mature and exhibit adult coloration.

What We Like About This Fish:

• Beautiful deep blue coloration in dominant males
• Peaceful disposition with fish and peaceful invertebrates
• Interesting social behavior when kept in colonies
• Safe with dwarf shrimp
• Will not harm plants

RECOMMENDED TANK PARAMETERS:

• Temperature: 68° - 82° F (20° - 27.7° C), but additional aeration/oxygenation is required at the high end of this range.
• pH: 5.5 - 7.0
• KH: 4 - 8 dKH
• Minimum Tank Size: 10 gallons for a single specimen or pair, 30+ gallons for a group

CARE INFORMATION:

• Diet: Omnivorous. Typically accepts some dry foods and frozen foods, but requires ample algae and biofilm for longevity. Bacter AE provides excellent biofilm growth for any biofilm grazing fish or invertebrates
• Social Behavior: Peaceful with other species, but multiple males may have minor squabbles.  Ample territory is recommended for multiple males
• Origin: Indonesia, Papua New Guinea, Solomon Islands
• Average Adult Size: 1.2 - 1.4 inches (3 - 3.5 cm)
• Average Purchase Size: 1 - 1.2 inches (1.3 - 2.5 cm)

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