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.
Professional aquascaper, Lea Maddocks writes about how a beginner can easily set up a planted tank in her article Setting Up a Successful Low-Tech Planted Tank like a Pro, Part 1: The Basics. While setting up a tank from scratch is perhaps the easiest way to create an aquascape, sometimes you have to work with what you have. Here Lea offers her advice for how to create a lush aquascape even if your existing tank has less-than-ideal conditions.
Difficult Livestock Choices
The hardness for African cichlids or brackish fish like mollies is often too high for many plants, though some species such as Vallisneria, Anubias, Bacopa, Elodea, hornwort, water sprite, some crypts, Sagittaria, and Java fern, among others, may still do well.
Many plants also will not tolerate colder water used for goldfish, danios, white clouds, or other more temperate fish, though Elodea, Vallisneria, swords, Anubias, Java moss, and hornwort will thrive. Research your desired plant species online and through plant specialists to know for sure what you can and cannot plant due to water chemistry and temperature limitations.
Less-Than-Ideal Grain Size
If your grain size is outside the ideal range of 2 to 5 mm do not be concerned, for here is a useful tip: You can use epiphytic plants, floating plants, plants already planted in floss, and potted plants. A well planted tank can be devoid of substrate if this tactic is used.
Epiphytic plants are those which do not need, or even like, to be planted, and instead need to be attached to driftwood, rocks or other ornaments with cotton thread where they will eventually secure themselves with roots used purely as hold-fasts. Such plants also require no nutrients from their roots, and absorb all they need via their leaves. Many also have the advantage of being adaptable to low or poor quality lighting, and are very hardy.
Floating plants are also an excellent option here, and many will thrive in almost any healthy tank as they have several advantages over submerged plants. The first is that they are very close to the light. Even with a weak lighting system, these plants will often get all the light intensity they need as they are usually less than inches away from the light source, and the light generally does not even have to penetrate the water to get to them. Do note that even with good intensity some plants can suffer if the spectrum is not correct, so check out my article for lighting advice. The second benefit of floaters is that in many cases the leaves actually sit on the surface exposed to the air, which is far richer in CO2 than the water. When this is the case, the limitation of dissolved CO2 is removed, and plants often grow well with nutrients obtained from fish and food waste.
If you are wish to plant non-epiphytic plants in a non-ideal sized substrate, planting in floss or potted plants may be the answer. Both of these approaches are simple. Wrap the roots of your chosen plants in a generous amount of filter floss, add root tab or fertiliser ball, and add another floss layer. These tabs/balls slowly release fertilisers and micro-nutrients to supplement larger root systems. Bury the lot gently within your substrate, and make sure to add a layer of your substrate over the top or some pebbles around the base to hide the floss and keep it weighted down. The roots will grow well in the floss, as they can penetrate it easily, though it is dense enough to provide a good structure for the root system. It is also porous enough to allow a great flow of oxygenated water and dissolved nutrients around the roots, and a large area for nitrifying bacteria.
It works in a way akin to plants in a hydroponic system. Once the plant is established, I find that there is usually no need to replace fertiliser tabs/balls the level of accumulated mulm will do the work for you. However, if your plants start to yellow or show other signs of deficiency, by all means add another tab—it certainly won’t hurt.
Alternatively, the same strategy can be used with pots for an interesting feature. Many kinds of pots, cups or containers can be used including terracotta, small bonsai pots, sake cups, or any ceramic pot which is dishwasher safe (dishwasher safe indicates that the glaze is safe and will not leech toxins into the aquarium water). Indeed, a well decorated tea-pot or cup could make a novel feature in your tank!
Jeff Senske’s (Aquarium Design Group) 90-gallon rimless aquarium features his signature hardscape-only design. He chose to use wild discus, penguin tetras, and gold tetras. Be sure to check out his articles on how he set up this tank. And here’s a gorgeous video by Jeff of the entire aquascaping process.