Circus Goby (Priolepis Nocturna) saltwater aquarium fish

Overview:

The Circus Goby is a small, active, bottom-oriented goby best kept in a mature, stable aquarium with plenty of structure. It does best in clean, well-oxygenated water, fine sand or smooth substrate, and lots of hiding places such as rockwork, driftwood, caves, and dense plants. Gentle to moderate flow is ideal, especially if the species comes from moving water or brackish coastal habitats. Because gobies are sensitive to sudden changes, stability matters more than chasing exact numbers; keep temperature, salinity if applicable, and pH consistent. A secure lid is important, as many gobies are capable jumpers. This species thrives when it has both open foraging areas and sheltered retreats, and it should not be housed in newly set up tanks.

Diet and Feeding:

Circus Gobies are opportunistic feeders and should be offered a varied, protein-rich diet. In captivity, they generally do best on a mix of high-quality frozen foods such as mysis, brine shrimp, daphnia, and chopped bloodworms, along with small sinking carnivore pellets or wafers. Live foods can be used occasionally to stimulate feeding, but should not be the only diet. Feed small portions once or twice daily, giving only what the fish can consume quickly. Because gobies often feed from the substrate, make sure food reaches the bottom. Uneaten food should be removed promptly to protect water quality. For young or newly imported individuals, smaller frequent feedings often improve conditioning and reduce stress.

Compatibility:

Circus Gobies are usually peaceful, but they can be territorial toward similarly shaped bottom dwellers, especially other gobies, blennies, or small benthic fish competing for the same cave or feeding area. They are best housed with calm, non-aggressive tankmates that occupy different levels of the aquarium. Suitable companions often include small tetras, rasboras, livebearers, peaceful rainbowfish, and invertebrates only if the goby is known to ignore them and the setup is appropriate. Avoid boisterous, fin-nipping, or highly aggressive species, as well as large predators that may intimidate or eat the goby. If keeping more than one goby, provide multiple hides and more space than you would for a single fish to reduce conflict. Compatibility is strongest in a well-structured tank where each fish can establish its own territory.

Health and Quarantine:

Like many gobies, this species is vulnerable to stress-related illness, especially from poor water quality, unstable salinity, and abrupt parameter changes. Common concerns include ich, bacterial infections, fin damage from aggression, and starvation in newly acquired specimens that fail to recognize food. Quarantine new arrivals for 2 to 4 weeks in a simple, cycled tank so you can observe feeding, monitor for parasites, and prevent disease introduction. During quarantine, offer varied foods and watch for rapid breathing, clamped fins, weight loss, or hiding more than usual. Preventive care should focus on clean water, regular partial water changes, careful acclimation, and a low-stress environment. Healthy gobies are alert, feed eagerly, and spend much of their time resting on the bottom while remaining responsive to activity around them.

algae spirulina mysis shrimp brine shrimp
Circus Gobies are small, bottom-oriented swimmers that spend much of their time perched on rockwork or hovering close to shelter, so they do best in a tank with plenty of hiding spots and protected resting areas. They are generally peaceful toward other species but can show mild territoriality toward conspecifics, especially in cramped quarters or when competing for preferred crevices. A minimum tank size of about 20 gallons is suitable for a single specimen, with a layout that uses rockwork and visual barriers to break lines of sight and reduce aggression. In community settings they usually coexist well with other reef-safe species, particularly quiet tank mates that will not outcompete them for food or harass their hiding places. Their diet is typically omnivorous, with a strong preference for small meaty foods and microfauna, and in the aquarium they readily accept frozen mysis, brine shrimp, and other finely prepared offerings. Because they are opportunistic grazers and pickers, frequent small feedings help match their natural hunting behavior and keep them in good condition.

FAQ

Frequently Asked Questions

About the Circus Goby

  • What tank size and water movement does a Circus Goby actually need, and why do they crash in “normal” community tanks?
    Circus Gobies do best in a cool, well-oxygenated, high-flow setup that mimics a fast stream. A single fish can be kept in about 10 gallons, but a pair or small group really does better in 20 gallons or larger with lots of broken sightlines, rocks, and caves. They are not a still-water goby; weak circulation, low oxygen, and warm temperatures are the main reasons they fail in hobby tanks. Aim for strong filtration, directional flow, and plenty of surface agitation.
  • Is the Circus Goby truly freshwater, or does it need brackish water like many other gobies?
    True Circus Gobies are freshwater fish and should not be kept in brackish water unless you are dealing with a different goby species entirely. They come from inland stream habitats, not estuaries. Adding salt “just in case” usually does more harm than good. Stable, clean freshwater with high oxygen and low to moderate hardness is the right approach.
  • What do Circus Gobies eat in captivity, and why do so many hobbyists report them as “picky”?
    They are carnivorous micro-predators and usually prefer small live or frozen foods over dry prepared foods, especially when newly imported. Best staples are blackworms, bloodworms, daphnia, baby brine shrimp, and chopped mysis. Many individuals ignore flakes or pellets at first because they are used to picking tiny prey off rock surfaces and streambed debris. Once settled, some will learn pellets, but they often still eat best when offered meaty foods in small portions multiple times a day.
  • Can Circus Gobies be kept with other fish, or will the males fight?
    They can be kept with tankmates, but choose carefully. Males can be territorial toward each other, especially in smaller tanks or when caves are limited. Good tankmates are peaceful, cool-water species that won’t outcompete them for food. Avoid fast, boisterous fish, fin-nippers, and larger predatory species. If keeping multiple Circus Gobies, provide several caves and visual barriers so each male can claim space.
  • How do you breed Circus Gobies, and what usually goes wrong with breeding attempts?
    Breeding usually happens in a cave or sheltered crevice, with the male guarding the eggs. The biggest mistakes are keeping them too warm, too still, or in a tank without enough hiding places. Condition them on live and frozen foods, keep water clean and well-oxygenated, and provide tight caves or tubes. After spawning, the male often tends the eggs until hatch. The fry are tiny and need very fine first foods such as infusoria, rotifers, or very small live foods before they can handle larger items.