Knight Goby (Stigmatogobius sadanundio) is one of the most visually arresting bottom-dwelling fish available in the hobby — a robust, silver-white body covered from head to tail in bold, irregular black spots, with an imposing first dorsal fin that males raise like a battle flag when claiming territory. The common name is well-earned: this fish carries itself with a watchful, deliberate intelligence that distinguishes it immediately from other gobies. Native to the tidal rivers, estuaries, and mangrove-lined creeks of South and Southeast Asia — from India and Sri Lanka through Thailand, Malaysia, and Indonesia — where it inhabits the brackish lower reaches where freshwater meets the sea. These specimens were collected from Singapore.
Feeding & Care Tip: Hikari Carnivore Pellets sinking to the bottom make an ideal daily staple — Knight Gobies are dedicated micro-predators that feed primarily at the substrate level. Supplement with Hikari Frozen Bloodworms, Hikari Frozen Mysis Shrimp, and Hikari Frozen Brine Shrimp 2–3 times per week. Avoid relying on algae wafers — this species is carnivorous, not an algae grazer.
Stigmatogobius sadanundio is a brackish water species that thrives with the addition of marine salt to achieve a specific gravity of 1.005–1.010 — roughly one tablespoon of marine salt per 5 gallons. Pure aquarium salt lacks the trace elements and buffering compounds found in marine salt mixes; use Instant Ocean or a comparable marine salt for best long-term results. In these conditions the Knight Goby's colors intensify and its immune system functions at its best. The species can adapt to pure freshwater but is significantly more robust and longer-lived in brackish conditions.
Each Knight Goby requires at least one cave or crevice to claim as its home territory — without this, these fish become stressed and reclusive. Provide more caves than fish: a pair needs at least four to six cave options so territories can be established without constant conflict. Terracotta pots, smooth rock caves, and sections of PVC pipe all work well. A fine sand substrate suits their natural habit of sifting through the bottom for food. Keep a tight-fitting lid — Knight Gobies are capable jumpers and will exploit any gap in the cover.
Best kept as a single specimen or a compatible pair in a species-appropriate setup. While multiple Knight Gobies can coexist in a large, heavily structured aquarium, they are territorial toward each other and toward other bottom-dwelling species. Ideal tankmates are surface or mid-water fish that do not compete for the substrate — mollies, halfbeaks, and larger rainbowfish all make excellent companions in a brackish community setup. Avoid slow-moving or long-finned fish, which may be nipped.
| Difficulty | Intermediate |
| Temperament | Territorial — Brackish Community |
| Typical Adult Size | 3–3.5 inches (7–9 cm) |
| Water Type | Brackish preferred (SG 1.005–1.010) — adapts to freshwater |
| Ideal Temp | 72–82°F (22–28°C) |
| Ideal pH | 7.2–8.2 |
| Ideal GH | 12–25 dGH |
| Staple Food | Hikari Carnivore Pellets; Hikari Frozen Bloodworms |
| Treat / Supplement | Hikari Frozen Mysis Shrimp; Hikari Frozen Brine Shrimp |
| Origin | Brackish estuaries and tidal rivers — South & Southeast Asia (Singapore) |
| Notes | Brackish water strongly recommended — use marine salt mix, not plain aquarium salt. Cave territories essential — provide more caves than fish. Carnivore — not an algae eater. Lid required. Males have extended dorsal fin rays. |
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