Knight Goby, also known as Stigmatogobius sadanundio, is a fascinating species of freshwater fish native to brackish and coastal waters of Southeast Asia, particularly found in regions like India, Bangladesh, and Myanmar. Here's some information about their lifestyle and care:

1. Appearance: Knight Gobies have a unique appearance characterized by their elongated body and pointed snout. They have a mottled brown or olive-green coloration with darker blotches or spots along their body. Their fins may have hints of red or orange. They grow to an average length of around 3 to 4 inches (7.5 to 10 centimeters).

2. Habitat: In the wild, Knight Gobies inhabit coastal estuaries, mangrove swamps, and tidal flats where freshwater and saltwater mix. They prefer areas with sandy or muddy substrates and plenty of hiding spots among roots, rocks, or vegetation.

3. Temperament: Knight Gobies are generally peaceful but can become territorial, especially during breeding or if housed with similar-looking species. They are known to be somewhat shy and may spend a lot of time hiding if they feel threatened or stressed.

4. Tank Requirements: A suitable tank for Knight Gobies should mimic their natural habitat. Provide a tank with a sandy or fine gravel substrate and incorporate plenty of hiding spots such as caves, driftwood, and live or artificial plants. They prefer brackish water conditions with a specific gravity ranging from 1.005 to 1.015.

5. Water Parameters: Knight Gobies are adaptable to a wide range of water parameters but prefer slightly brackish water conditions. Maintain the temperature between 75°F to 82°F (24°C to 28°C) and a pH range of 7.0 to 8.0. Regular water changes are essential to keep the water quality high.

6. Diet: Knight Gobies are omnivorous and will accept a varied diet in captivity. Offer them a combination of high-quality sinking pellets or flakes, frozen or live foods such as bloodworms, brine shrimp, and small crustaceans. They may also graze on algae and detritus in the aquarium.

7. Compatibility: Knight Gobies can be kept with other peaceful brackish water species such as mollies, bumblebee gobies, archerfish, and monos. However, avoid keeping them with aggressive or fin-nipping species that may harass them.

8. Breeding: Breeding Knight Gobies in captivity can be challenging due to their specific habitat requirements and the need for brackish water conditions. If you're interested in breeding them, provide a separate breeding tank with suitable spawning sites and gradually increase the salinity of the water.