Brackish-intolerant Aquarium Fish

Freshwater Fish

Obviously the best fish for a brackish water aquarium are fish that naturally come from brackish water, but it often happens that an aquarist wants to mix some brackish water species into a regular community tank (or vice versa). For the most part this is a bad idea -- most of the commonly traded community fish are not salt-tolerant and will not do well in brackish water. With a very few exceptions, tetras, barbs, danios, rasboras, gouramis, and loaches should not be kept in the brackish water aquarium.

Catfish are a mixed bag in terms of salt-tolerance. There are of course several families with species that enter the sea, including the Aspredinidae, Ariidae, Bagridae, Pangasiidae and Plotosiidae. But the two families most frequently kept by aquarists are the Callicthyidae and the Loricariidae, and these families are made up almost entirely salt-intolerant catfishes.Corydoras species as well as most of the plecs and bristlenose catfish should not be kept in the brackish water aquarium. Exceptional members of these two families include some species of Hypostomus such as Hypostomus plecostomus known to be slightly salt-tolerant (SG to 1.005) and the brown hoplo Hoplosternum littorale, a species commonly found in brackish water in the wild and easily maintained at SG 1.005 or even slightly higher.

Some cichlids are quite salt tolerant, of which more is said elsewhere in this FAQ, but the Rift Valley cichlids apparently react badly to brackish water, succumbing to “Malawi Bloat”, a potentially fatal dropsy-like condition. Cichlids from soft water environments, including angelfish, are equally intolerant of salt.

Livebearers and killifish from hard, alkaline waters often do fine in slightly brackish water. So while things like platies, goodeids and pupfish might not come from brackish waters in the wild, they can be expected to adapt successfully to a specific gravity as high as SG 1.005.

Marine Fish

Some traded marine fish will tolerate low salinity conditions for extended periods, even indefinitely, but in general this should not be assumed. If you want to add marine species to your brackish aquarium, do your research carefully and make absolutely sure the species being offered in the shop is what you think it is.