A Knight of The Aquarium Realm
We have a question for you, that we've pondered both publicly and among ourselves. How is it that Stigmatogobius sadanundio got its most prevalent common name, the Knight Goby? Did it kneel before the Queen? We find this unlikely, given its lack of legs. Did it serve as a squire? Also, unlikely as it would be difficult to carry armor without arms. So, it is almost certainly not the normal pathway, and it certainly isn't based on it having a fighting attitude with most fish. Whatever it may be, chat to us about it on our socials, let's see what you've got. Interestingly, it doesn't really have any other often used common names in English. We are fond of the German name for it though, they call it Gefleckte Grundel, which translates as “Spotted Goby” which makes sense when you look at it but isn't as fun to say in English.
These are very pretty little fish. They don't get much bigger than three or four inches long, with mostly white (sometimes light gray) bodies that are flecked with little black spots, they have striking dorsal fins reminiscent of a miniature roosterfish that will also sport an electric blue spot when mature.
In the wild, Knight Gobies come from the lower reaches of freshwater streams, occasionally from brackish water. These streams are sometimes only inches deep. The wild range is spread throughout southeast Asia; they can be found in India, Pakistan and Sri Lanka, but also through Myanmar, the Malay Peninsula, Thailand, Singapore, Cambodia and coastal Sumatra.
As a result of these wild conditions, these fish do best in aquariums that feature a trace of salt, and we mean a trace, specific gravity of 1.005 or less. They don't need brackish conditions, but if you're going to keep them in a full freshwater display, avoid water that is acidic and/or overly soft. Shoot for water chemistry that features a pH between 7.5 and 8.5 with hardness between 10-20 GH. Temperature wise they'll be fine anywhere between 68 and 78 degrees (obviously Fahrenheit.)
The display for a Knight Goby needn't be overly large; 20 gallons or so would be fine for one of them. More Gobies could be kept together, but they'd need more space (not depth) to allow each Goby a territory to establish. They'll love a bunch of cover in the way of caves and rocks to hide in and work around. They are naturally nocturnal fish and will be more active during the day if the lighting for the aquarium is dim. They can be kept in planted tanks, but like to dig and move substrate around, so plants will need to be affixed to décor, and the plants you choose will have to be suitable for the conditions your Goby needs. Substrate should be a relatively fine sand. They don't leave the bottom of the display often, so a cover isn't really relevant. Floating plants could also be used to reduce light in the tank.
Knight Gobies are very easy to feed, and will accept a wide range of meaty foods, and are usually no problem when it comes to getting the to take pellets. Here we give them a mix of meaty foods from Gamma including Mysis, Brine (and all the different “Brine Plus” products they offer), as well as Bloodworms, Tubifex and Mosquito Larvae, and unsurprisingly, they'll relish any opportunity to have these foods live as well. They are known to do a bit of grazing on any algae you may have in the aquarium, so we make sure that one of the Brine Shrimp we regularly use is the Brine Plus Spirulina. As a fish that is primarily nocturnal in the wild, you may have to feed them at lights out and just before lights on initially. Here we feed them twice a day, but once a day would be fine too as long as they got enough food at each meal.
Stigmatogobius sadanundio is a great and unusual addition to the community aquarium as long as you make good tankmate choices. There are really only a couple caveats. One is that these fish are predators and won't miss an opportunity to eat a smaller and unwary fish. The other is that they might be territorial with fish that act / look similarly if they are in too crowded of a space. Other than that, they are going to completely ignore most fish. Good tank makes would be things that like a similar water profile like the super adaptable Mollies, there's a variety of catfish and Rainbowfish that could work, as well perhaps Monos if you're thinking about a dedicated brackish tank. They'd be an amazing addition to an Archerfish display too.
If you end up with a male and a female, there is a chance they could breed in your aquarium. There are some documented reports of successful reproduction in hobbyist's aquariums, but they are rarely, if ever commercially aquacultured, so there isn't much public information on the topic other than that they are cave spawners (which makes sense, as they love a cave.) There is little or no parental care after the eggs hatch, which means they are likely to consume the young. As an “amphidromous” species or one that can migrate between fresh and saltwater, there is a chance that salinity will play a role in triggering spawning. There is an excellent challenge here available for the experienced aquarist to break some new ground if you can find a way to do this consistently!
These little fish are pretty to look at and a delight to watch as they dart around their homes in search of food. When first added to the tank, they're likely to be shy, but they'll become more and more active during daylight as they get used to getting most of their food then. They are one of the most unique bottom dwellers you can have in a freshwater aquarium. So, if that's something you're interested in having in your tank, or if you are just an aquaculture trailblazer looking for a new obsession, maybe think about making a Knight Goby the defender of your aquarium realm! Ask your LFS to get you one from Aquatropic today!