#mid brackish

Maximum Size: 18" Aggression: Low Temperature: 73-77 F pH: 7.5-8.5 Hardness: 10-25 dH Brackish Tolerance: 1.000-1.010, 1.003-1.005 best Minimum Tank Size: 55 gallons Feeding: Frozen and live foods about the size of Brine Shrimp, dry algae-based foods like algae wafers/pellets Notes: The Peruvian Eelgoby is very similar in appearance to the closely related Violet Goby (G. broussonnettii), though the Violet Goby possesses violet bands down almost to the tail whereas the Peruvian Eelgoby may only possess violet patches on the head and/or along the lateral line. Either are sold as the “Dragon Goby”, however G. broussonnettii is the predominant species in the US and G. peruanus is the more common species in the UK (and perhaps elsewhere in Europe).

The Peruvian Eelgoby is fairly peaceful, despite its size, and do not bother tankmates aside from being somewhat territorial. They may quarrel with conspecifics, though, and groups of these fish should be kept in very large tanks (100+ gallons). They feed by sifting through the substrate and using their teeth to scrape algae. Food is best offered when dark (at nigh or early morning) and multiple feedings per day is beneficial. Not being very active fish, they are best left without food competition from the likes of Catfish and Loaches. Hand feeding is a good practice.

Unlike the related Violet Goby, these fish can do well in freshwater tanks, provided the water is very hard and very clean. They are better kept in low end brackish tanks, however, and do not appear to adapt to higher salinity levels.  These fish prefer dim tanks and do best with several caves to hide in.

Sources

Maximum Size: 12" but 5″ more likely Aggression: Low Temperature: 74 - 82 F pH: 7.5-8.5 Hardness: 15-25 dH Brackish Tolerance: 1.000-1.015, 1.005-1.010 best Minimum Tank Size: 40 gallons for average sized adult, may require up to 125 gallons Feeding: Frozen and live foods are staple of diet. Brine and Mysis shrimp, pieces of earthworms, chopped shellfish. Not guaranteed to switch to dry foods. Notes: The largest of the fish sold as “freshwater soles”, Oriental Soles can indeed live in hard, alkaline freshwater but are most reliably kept in mid brackish conditions.

Like other flatfish, Oriental Soles typically spend most of the day buried in the substrate with only eyes showing. Though it will attempt to burrow in just about any substrate, sharp ones like gravel or some sand types (like Tahitian Moon Sand, a glass by-product) are likely to scratch them up and can lead to illness. Your best choice is to use something soft like silica sand or sugar fine aragonite. Other tank decor is largely immaterial. Plants, plastic or otherwise, are likely to be uprooted and are best when weighted down.

Non-aggressive fish, Oriental Soles can be kept with many types of peaceful tankmates but are still likely to eat bite sized fishes like the smaller livebearers. Nippy fish like puffers should also be avoided as Oriental Soles are easy targets (especially their eyes). To reduce competition for food, they are best fed at night just after the lights go off.

Sources

Freshwater Soles (family Soleidae and others), Neale Monks

Giving your aquarium some sole: Success with fresh and brackish water flatfish, Neale Monks

Tonguefish (Brachirus panoides), The Aquarium Wiki

Brackish Livestock Selection, Neale Monks

Maximum Size: 12" Aggression: Mid Temperature: 73-77 F pH: 7.5-8.5 Hardness: 15-25 dH Brackish Tolerance: 1.005-1.025, 1.010-1.015 best Minimum Tank Size: 60 gallons alone, 125 gallons or more for tankmates Feeding: Live Shrimps and Earthworms, can eventually be weaned onto frozen foods like krill, shrimp, pieces of fish, and chopped shellfish Notes: Sold as the Freshwater Toadfish, the name “Grunting Toadfish” is a lot more accurate. The adult males are surprisingly loud with their attempts to attract females. Keeping these fish in groups may help to a degree with the noisiness. Though they do superficially resemble Waspfish (family Tetrarogidae), these fish are not venomous.

Grunting Toadfish are generally inactive in the home aquarium. They spend most of the day hiding in rockwork or under a thin layer of substrate and are more active at night. Lighting in the tank should be subdued. Though predatory, they are not especially aggressive fish. Large, non-aggressive fish like Scats, Monos, and Green Chromides are all good choices, as are the larger Archerfish. These are extremely adept hunters and are too likely to eat tankmates smaller than they are. Any fish under 75% of the Toadfish’s length are likely to be eaten unless they are also very tall like Monos or Batfish.

Getting these fish to accept frozen foods can be challenging at first. Success has been noted by using a stick and moving them back and forth in front of the Toadfish to simulate swimming. Those that are slow to make the transition may be fed feeder shrimp or earthworms until they associate their owner with food.

Sources

Brackish for Beginners 2: Big But Beautiful: A Southeast  Asian Estuary, Neale Monks

FAQs on Brackish Water Livestock Selection, Acclimation, Wetwebmedia

Grunting Toadfish (Allenbatrachus grunniens), The Aquarium Wiki

Maximum Size: 4" Aggression: Low Temperature: 74 - 82 F pH: 7.5-8.5 Hardness: 15-25 dH Brackish Tolerance: 1.000-1.025, 1.003-1.010 best Minimum Tank Size: 30 gallons Feeding: Frozen and live foods are staple of diet. Brine and Mysis shrimp, pieces of earthworms, chopped shellfish. Not guaranteed to switch to dry foods. Notes: One of the species sold under the moniker of “freshwater soles”, these fish can indeed live in hard, alkaline freshwater that is kept immaculately clean but are more likely to thrive in at least low end brackish conditions. Among the freshwater soles, the Pan Sole is both the smallest and the most elongated of the species offered.

Like other flatfish, Pan Soles typically spend most of the day buried in the substrate with only eyes showing. Though it will attempt to burrow in just about any substrate, sharp ones like gravel or some sand types (like Tahitian Moon Sand, a glass by-product) are likely to scratch them up and can lead to illness. Your best choice is to use something soft like silica sand or sugar fine aragonite. Other tank decor is largely immaterial. Plants, plastic or otherwise, are likely to be uprooted and are best when weighted down.

Non-aggressive fish, Pan Soles are not taken to eating adults of even smaller species like Guppies and thus are fairly safe tankmates for a wide variety of peaceful fish. Though not social animals, they do seem to get along when kept in groups. Nippy fish like puffers should also be avoided as Pan Soles are easy targets (especially their eyes). To reduce competition for food, Pan Soles are best fed at night just after the lights go off.

Sources

Freshwater Soles (family Soleidae and others), Neale Monks

Giving your aquarium some sole: Success with fresh and brackish water flatfish, Neale Monks

Tonguefish (Brachirus panoides), The Aquarium Wiki