TFH Magazine Blog

A Brackish Paludarium

Mudskipper (Periophthalmus barbarus). Photograph by MP. & C. Piednoir

By Joshua Wiegert

Brackish-water fishes are some of the most interesting and unique fishes available to the aquarist. At least three types of brackish fishes make perfect addition to the paludarium. The most obvious of these are the various mudskippers.

Mudskippers are small gobies that have evolved the ability to exit water. They are typically found in intertidal areas—tide pools and the like—where water levels vary dramatically throughout the day. They resemble a fantasy version of what we imagine the first animals to conquer land might look like. Evolutionarily, mudskippers evolved recently; they are not remnants. However, they may give insight as to how animals first conquered land. In the aquarium, they may be fed small crabs, shrimp, crickets, and various frozen foods.

Another option is archerfish. Maintaining the archer fish in a paladurium gives the aquarist the potential opportunity to witness one of the most fascinating feeding mechanisms among fishes. When archer fish locate a prey item on an overhanging leaf, branch, or other terrestrial structure, they spit a quick stream of water at it. The prey item falls into the water, where it is eaten.

An archerfish paludarium. Photograph by Abe Schwartz.

Lastly, the four-eyed fish (Anableps spp.) are brackish water fish that have developed a split eye structure allowing them to see both above and below the water. They cruise along the surface of the water, their eyes held at the water line. This allows them to locate surface prey items, such as insects, and avoid predators from below.

Four-eyed fish (Anableps anableps). Photograph by Edward Taylor.

All of these are brackish water fishes, which means they cannot survive in a standard freshwater aquarium. They require approximately marine salt in their water to survive. Unfortunately, this greatly limits the number of available plants–salt and plants tend not to mix well. There are a number of salt-adapted plants, though these are seldom available to hobbyists. The seagrape (Coccoloba uvifera) is occasionally available at plant nurseries near costal areas, unfortunately at a rather large size. Fortunate hobbyists may be able to collect some shoreline plants, though check on the legality of collecting before you head out.

The best plant for aquarists to try, however, is the red mangrove (Rhizophora mangle). This plant has become a staple in the marine hobby, where it is grown paludarium style. Propagules are typically sold and they look like a large green bean. They may have some roots on the bottom, and some leaves at the top. Given time, they will quickly develop into a small tree, which must be trimmed to keep to a small size.

Mangroves can be grown in everything from brackish water to full seawater. Photograph by Nicholas Violand.

Mangroves can be slipped through the mesh of egg crate, though this will restrict their growth over time. More simply, the roots can be anchored to a large rock with fishing line, rubber bands, or the like until they develop a hold. A simple solution is to take a square of hard foam (ask your local fish store for a fish box) and cut a hole through it. Pushing a pen or a screwdriver through it will work just fine. Gently slip the leaves through the hard foam (be careful not to break them), and let it float. Once anchored, the foam can just be cut away, or the holes simply widened to allow growth.

Despite rumors to the contrary, mangroves can be grown in pure saltwater, brackish water, or even straight freshwater—I’ve put them outdoors in tubs during the summer.

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