Like the hundreds of species of Gobies and Goby-like fishes found in marine environments, the fresh and brackish gobioids are demersal (bottom dwelling), retiring versus outgoing, generally lack a gas-bladder (no need sitting on the bottom) sharing other internal structural similarities as adaptations to a mostly sedentary existence. See the above link to the Gobioids en toto for a rundown on this super-groups taxonomy.
Suborder Gobioidei; Eight families, about 268 genera, 2100 species (many more to be described). A listing here just of families with fresh to brackish water members.
Family Eleotridae , Sleepers. Marine, fresh and brackish water species. Have separated pelvic fins (no sucking disc). Mouths never sub-terminal. To two feet in length! Approximately 35 genera, 150 species.
Family Gobiidae; Gobies. Mostly marine, but some fresh, brackish species. Four families, of about 212 genera, 1900 and counting species.
Subfamily Amblyopinae; worldwide assemblage of gobiid fishes found off estuaries and in rivers. For aquarists, includes the "Violet Goby", aka "Dragon Eel", Gobiodies broussoneneti.
Subfamily Ocudercinae; Mudskippers. Live in Mangrove swamps, mudflats from Africa east to Samoa. Ten genera (e.g. Apocryptes, Boleophthalmus, Brachamblyopus, Gobioides, Taeniodes, Trypacuchen), about 34 species.
Subfamily Gobionellinae. 56 genera, many freshwater species. Including amongst the most popular brackish aquarium species, the tiny, gentle Bumblebee Gobies (nine species) of the Genera Brachygobius and Hypogymnobius. A few species are offered as "the" Bumble Bee Goby: B. nunus, amongst the others below.
Family Rhyacichthyidae, the Loach Gobies. Freshwater streams of the Indo-Australian Archipelago, Philippines, China, the Solomons. Have depressed heads, compressed tails, underslung mouths that sport a fleshy upper lip; small eyes, widely separated pelvic fins. Use these traits to cope with fast-movng water, fins, body shape, mouth to hold onto hard surfaces... To nearly thirteen inches in length. One genus, Rhyacichthys, with two species.
There are other families containing freshwater, brackish gobioids.
Brown, Stanley. 1996. Gobies. V.4, #1 96 The J. of Maquaculture, The Breeder's Registry.
Hunziker, Raymond E. 1985. Gobies for freshwater and brackish aquaria. TFH 12/85.
Nelson, Joseph S. 1994. fishes of the World, 3rd ed. John Wiley & Sons, NY. For systematic reviews.
Castro, Alfred D. 98. Knight Goby. How to keep 'em and how to breed 'em. AFM 6/98.
Kurtz, Jeff. 2000. The Knight Goby. A good reason to go brackish. TFH 11/00.
Schofield, Diane. 1965. Busy little bees. TFH 1/65
Tomey, William A. 1969. The Grey Pearl of Siam. The Aquarium. 8/69.
Anon. 1982. A Peacock out of paradise. Aquariums Australia 2:3, 82.
Lange, Gary. 2000. Modern masterpiece- The Peacock Gudgeon. A tiny work of art. AFM 6/00.
Rosler, Hans Jurgen. 1997. The care and breeding of Tateurndina ocellicauda. TFH 2/97.
Schreiber, Roland. 1995. The Fiery Sleeper. TFH 9/95.
Tappin, Adrian R. 1998. The Empire Gudgeon. FAMA 1/98.
Walker, Braz. 1970. The Spotted Sleeper. The Aquarium 4/70.
Dingerkus, Guido and Bernard Seret. 1992. Rhyacichthys guilberti, a new species of Loach Goby from Northeastern New Caledonia (Teleostei: Thyacichthyidae). TFH 7/92.
Hansen, Pamela and Jorgen. 1979. The Mudskipper. TFH 7/79.
Lass, David. 2001. Mudskippers. A fish becoming an amphibian. AFM 2/2001.
Lucanus, Oliver. 1998. A fish out of water- Mudskippers. TFH 3/98.
Mancini, Alessandro. 1991. Mudskippers in nature and captivity. TFH 6/91.
McGregor, Glenn. 1999. Mudskippers: like a fish out of water. FAMA 4/99.
Murdy, Edward O. 1986. Mudskippers of Malaysia. The lords of the mudflat.FAMA 11/86.
Norris, T.L. 1984. A community Mudskipper tank. FAMA 9/84.
Ono, Dana R. and Debra Sponder. 1982. Table-top Mudskippers. FAMA 10/82.
Schwartz, Gerd. 1975. The Mudskipper. Aquarium Digest Intl. 3:4, 75.
Sidley, Rodney. 1984. Keeping Mudskippers. FAMA 12/84.
Taylor, Edward C. 1997. Mudskipper environment. Pet Business 11/97.
Volkart, Bill. 1996. Mudskippers: Demanding by rewarding. TFH 5/96.
Violet Goby, Dragon Eel:
Boruchowitz, David. 2001. A sickly dragon. TFH 2/01.
Harper, Rodney W. 1995. Captive care and maintenance of the Violet Goby, Gobiodies broussoneneti. TFH 7/95.