The knight goby, also known as stigmatogobius sadanundio, is a popular tropical brackish water aquarium fish ideal for experienced aquarium keepers. This article will show you how to care for knight gobies, maintain their habitat and provide the best breeding conditions.
The knight goby or knight fish is popular because of its attractive appearance and territorial behavior. Their body color ranges from a muted silver to light gray with black speckles behind the gill plate to the tail. The pectoral, anal, and tail fins have white lines on their fringes. The dorsal fin has a large splash of black.
You can tell males and females apart a couple of ways. Adult males tend to have longer pectoral and tail fins and slimmer, muted gray or silver bodies. Females tend to have rounder bodies, shorter fins and will usually develop a yellowish coloring once settled into an aquarium.
In temperament, the knight goby is part reclusive and part bravado. During daylight or in bright tanks, they stay hidden in their shelters. In the dim light and at night, they will venture forth to sift sand for food and defend their home territory from their tank mate rivals.
Knight Goby Stats
|Genus & Species:||
|Size:||Up to 3″ (8cm) Total Length|
|Habitat:||Asia: India, Sri Lanka and the Andamans to Singapore and Indonesia.|
|Min Tank Size:||20 + gallons|
|Diet:||Prefers live but will take most flake, frozen, dried or sinking pellets.|
|Water:||Temperature: 72°F to 81°F (20-26°C) pH range: 7.0 – 8.0; dH range: 9 – 19|
|Salinity:||A 1% addition of salt is recommendedas these fish are found in brackish water.This can be accomplished by adding 7.5 TSP of sea salt/ 10 gallons (10g/10 L) on a hydrometer the reading should be between 1.005 to 1.010 specific gravity.|
|Communities:||Not with large agressive fish, will eat smaller fish.|
Listed tank size is the minimum
|Size:||Up to 3″ (8cm) Total Length|
7.5 to 8.5
|Hardness:||Medium to hard. Range: 9.0 to 19.0|
|Temperature:||72°F to 81°F (20-26°C)|
Knight Goby Care
While the salinity may differ, you must select and maintain a static salinity level. This will ensure to keep the habitats healthy in an aquarium. Brackish water aquariums share characteristics of both fresh and saltwater tanks. The benefit of this is that it’s easier to take care of than a pure saltwater tank because both fresh and brackish water fish can do well in that environment.
A 20-gallon tank should be considered the minimum to keep a knight goby or two in addition to tank mates. It is an ideal way to keep a greater variety of hardy species. It is the most suitable habitat for the knight goby.
Suppose you consider that ocean water’s basic salinity is 25 to 35 parts per thousand with a specific gravity of 1.025 and freshwater has a specific gravity of 1.000. In that case, an excellent brackish water mix will have a particular range of gravity of 1.005 and 1.012.
You should maintain alkalinity between 10° and 20° dKH (180 ppm to 360 ppm). Try to keep pH levels between 7.5 – 8.5. The ideal temperature range is 68-78°F (20-26°C).
Knight gobies are tolerant to ranges of salinity but are not tolerant of stale and stagnant water. A good rule to follow is maintaining good filtration and changing 10% of the water every week or 25% every two weeks. Be sure to treat tap water and condition it to the proper salinity and other levels before adding it to the aquarium.
As knight gobies are both shy and territorial, they do best when giving them ample places to hide. This is an excellent opportunity for you to get creative with your aquarium design.
In their native environments, knight gobies will seek out small caves, ledges, and similar structures for their homes. Since they are sand sifters, an aquarium with a sandy bottom is highly recommended and more in line with their native habitat.
Starting with a good sand base, arrange rocks, aquarium décor, or things like small flower pots to give your knight gobies places to hide. If you plan on having more than one knight goby in the aquarium, place the hiding spots far enough apart so that they each have their territory.
Things like freshwater weeds and grasses will not do well in brackish tanks, so you are better off using plastic plants. Try to avoid using driftwood to leach tannins into the water and have an adverse effect on tank alkalinity and pH.
To avoid interspecies conflicts, you should not have more than a few knight gobies in a standard-size aquarium. When selecting fish, pick an even match of males and females if you want to establish breeding pairs.
If you provide ample cover for them, knight gobies should be able to coexist without picking on each other over territorial disputes. During low light periods, you will often see them poking their heads out of their hiding places or exploring their aquarium territory. Keeping the tank dimly-lit will encourage them to be more active.
Knight Goby Breeding
Knight Goby breeding is one of the more challenging feats in tropical brackish water fish keeping. The task is complicated by the knight goby’s territorial nature and the static nature of aquarium conditions. If you can get your knight gobies to breed, you are a skilled tank keeper indeed.
The two things you can do to encourage breeding are to modify the water temperature and increase the water salinity.
To help your knight gobies get in the breeding zone, try warming the water to 75–82 °F (24–28 °C) with a standard aquarium heater. Regardless of if you have a fresh or brackish water tank, consider modifying the salinity to about ¼ marine strength or specific gravity of 1.005sg. Other species of estuary fish will spawn in response to a decrease in salinity in the water. If you usually keep a brackish tank, try increasing the ratio of freshwater.
Knight gobies are shelter spawners. After an elaborate courtship, the female will lay eggs on the ceiling of the shelter you have placed for them. A breeding pair can produce as many as 1,000 eggs.
Be careful not to dislodge the filmy strings if you do a deep clean on the tank. Male knight gobies usually care for the eggs until they hatch, then abandon their parental duties. If you have other knight gobies in the tank, they will try to eat the fry.
Once the eggs have hatched, it is recommended you transfer the fry as soon as they reach a catchable size. Small brine shrimp or sinking flakes are good food for knight goby fry.
Knight Goby Tank Mates
While knight gobies are not active predators, some care must be taken when adding other aquarium species. They will chase and nip other fish that get down to their level. The best knight goby tank mates are species that live in the aquarium’s mid or upper region.
Species that do well with knight gobies include:
- Skunk Goby
- Red Scat
- Bumble Bee Goby
- Silver Scat
- Butterfly Leaf Goby
- Mono Sebae
- Target Fish
- Mono Argentus
- Archer Fish
- American Flagfish
- Indian Glassfish
- Green or Orange Chromide
Species that can badger or prey on knight gobies include:
- Ceylon Puffer
- Colombian Shark Catfish
- Golden Puffer
- Fugu Puffer
- Spotted Puffer
If knight gobies have an opportunity to gobble up smaller fish, they will take it. They will also nip at long, wavy fins and slower fish that stray into their territory. On the other hand, larger aggressive species such as cichlids or Columbian sharks will badger or prey on knight gobies if they get the chance.
Keep your aquarium with similar-sized, less aggressive species that live in different levels. You will have a happy and well-balanced tank.
Knight Goby Diet
The good news is that maintaining a good knight goby diet is effortless. Knight gobies are not fussy eaters and will eat anything they can get into their mouths. The not-so-good news is that you must take care that their tank mates don’t wind up on the dinner list.
Since knight gobies live near the tank’s lower strata, feeding them means using foods that will sink quickly past other fish in the aquarium to the bottom. They do like traditional fish foods like freeze-dried flakes. But since flakes will float until they gain enough water to sink, flakes can be gobbled up by the upper and mid strata knight goby tank mates before making it down to the knight fish feeding zone.
Good food choices are sinking frozen or dried pellets, brine shrimp, and any feed worm to combat this. They also like live foods such as brine shrimp. Knight gobies are true omnivores and will even nibble on green algae if it is present near their hiding places.
- Maintain a brackish tank environment that mimics the knight goby home waters.
- Keep the aquarium water fresh and clean.
- Tankmates should be the same size and aggression level.
- Increase water temperature and salinity to encourage breeding.
- Sinking live, dead, or pelletized food will keep them fed.
A well-established brackish tank will support knight gobies for years. Knight gobies or stigmatogobius sadanundio are a challenging species that will provide exceptional variety and rewards for advanced aquarium keepers.