Mangrove Riparium Journal – Article #1 of 4

by Devin Biggs

Introduction

This article is the first in a short series that I will use to document the design and development of a unique kind of aquarium, a planted riparium featuring mangrove habitat fish and plants in brackish water. Brackish water may seem to limit choices for plants and livestock, but there are many fascinating possibilities for this kind of setup. Riparium growing methods are a good solution for growing the most intriguing plants of mangrove swamps and estuary environments in an aquarium.

I will write about this project in four different articles:

1. Aquarium design concept
2. Plant selection and growing
3. Fish selection and stocking
4. Progress over time

This first entry will describe the general project concept and it will also include details on the planting accessories and other features of the aquarium setup. Below, the propagules (seed-like reproductive structures) of black mangrove (Avicennia germinans).

Planted Ripariums: Planted ripariums are a new kind of aquarium display that feature emergent aquatic plants, species that are rooted in the wet substrates at the edges of ponds, lakes, rivers and streams, but hold their foliage up in the air. Hanging riparium planter cups and rafts support the plants up at the waterline in the riparium display. The picture below shows a riparium planting with emergent plants and fish. This setup used freshwater and was planted into a 55-gallon tank.

Ripariums are somewhat less complicated to build and maintain in comparison with paludariums, which they resemble, because the planters and plants are modular and easy to move around in the aquarium. Paludariums, in contrast, use built-up terrestrial features (boulders, driftwood, foam or plastic forms) to support the plants. While paludariums and similar kinds of setups can make good homes for turtles, frogs and other amphibious animals, ripariums are less suitable for these creatures because there is no real land area for them to use. Nevertheless, ripariums are excellent habitats for aquarium fish, which benefit from the natural cover and robust filtration offered by the plants. A wide range of beautiful emergent aquatic plants grow very well in riparium setups and add further interest to the aquarium display.

The riparium growing method has been developed during the course of just the last few years by hobbyists and product developers in the United States. The next picture shows a riparium hanging planter with a clay-based plant gravel.

The mangrove habitat in nature: Although I want this project to be a realistic representation of the mangrove swamp environment, I am not trying to create a strict biotope display to represent one specific geographic area. Rather, I am going to include brackish water species from different areas that I can find in the hobby and that can live together in a compatible way. Although may can share many of the same environmental conditions, mangrove habitats in different regions have distinct assemblages of plant and animal species.

Mangrove habitats are found in coastal areas all around the world in tropical and subtropical regions. They are characterized by brackish (moderately salty) water, a unique kind of environmental situation that results from the mixing of freshwater and saltwater where rivers and other freshwater sources meet the sea. Mangrove swamps are especially likely to occur in estuaries, the areas at the mouths of rivers where the water level and water mixing are influenced daily by the ocean tides. Mangrove swamps are dominated by trees, whereas other kinds of brackish/estuary habitats, such as grassy saltmarshes might feature other sorts of plants. The brackish water mangrove/estuary environment creates special challenges and unique opportunities for plants and animals. The unique adapations of brackish environment species are fascinating to observe in an aquarium. Below, a coastal mangrove swamp in Florida, USA.

Brackish water species need to be able to flourish in moderately salty water, but they must also withstand the changes in salinity levels which can result where the freshwater and seawater are mixed in different proportions, as influenced by storms, tides, proximity of the sea and seasonal fluctuations in river flow. The rivers that feed estuaries deposit great quantities of muddy sediments. The nutrients in mangrove swamp mud can support highly productive plant growth, but the intense bacterial activity in the mud can also lead to severe oxygen depletion, a very difficult situation for plant roots. Some kinds of mangrove trees have unique root adaptations, such the prop roots of red mangrove (Rhizophora mangle) or the pneumatophores of black mangrove (Avicennia germinans) that reach above the mud and are thought to help the roots to uptake more oxygen.

The fishes of mangrove swamps have other remarkable adaptations to this productive, yet difficult kind of habitat. Archerfishes (Toxotes sp.) have the unusual ability to capture terrestrial prey by shooting jets of water at insects that crawl on the limbs of mangrove trees. Mudskippers (Periophthalmus and other genera) use the tide-influenced mangrove environment very well with their amazing abilities to walk about on land and climb trees. Among many other fascinating and beautiful brackish water, aquarium-suitable fishes are the sailfin molly (Poecilia latipinna), Celebes rainbowfish (Telmatherina ladigesi) and orange chromide cichlids (Etroplus maculates).

Aquarium Design Concept

Aquarium Hardware and Life Support: While deciding upon an aquarium size and shape I wanted to choose a tank with plenty of swimming room for fish and growing space for plants. I settled with using a 30 breeder, a popular, economical and easy to find model that is especially nice for creating a “pond style” riparium with water filled all the way to the top and with plants growing in the area above. I really like the visual effect of this kind of riparium. Here is a quick shot of the tank where I have it set up in a corner of my basement fishroom.

A 75 watt Eheim Jäger will heat the tank, while a Fluval U Series submersible filter will provide filtration and water circulation.

This kind of riparium setup requires a pendant light fixture so that the plants can have enough vertical space to grow. Until a few years ago the options for pendant aquarium lighting were relatively costly and hard to find, but the recent popularity of the bright T5 strip lights and reflectors used for hydroponic growing has made it much easier and more economical to set up this kind of lighting. For this display I plan to start out with a single 39-watt HO T5 striplight. For the time being a rustic plywood (see below) mount will hold the light, but I later I will upgrade to a double-strip T5 fixture with more attractive hardware.

Substrates: Many mangrove estuary habitats are characterized by deep, dark muddy substrates, but I have also seen mangroves in Florida growing in white beach sand. The abovewater riparium plants in this tank will tend to shade the underwater portion of the display, so I decided to use a white aragonite reef aquarium sand to cover the bottom and brighten the underwater area. Aragonite would be a poor choice for most kinds of planted tanks, especially setups with CO2 injection, which would tend to cause its rapid dissolution, but it shouldn’t cause any trouble at all for this model ecosystem. I aragonite in reef aquariums and I think that it will make nice effect in this display too.

I will build the layout hardscape with several good-sized manzanita stumps. I started these driftwood pieces soaking in the tank so that they could begin to leach some of their water-staining organic compounds and so that they would sink for easier positioning in the riparium layout. The aragonite sand will also make a pleasing contrast against the dark features of these manzanita driftwood stumps.

The mangrove trees and other plants will be rooted in the riparium planters in a nutrient-rich plant substrate. Nothing will be planted directly into the aragonite sand. The picture below shows one of the riparium hanging planters (Available from: www.RipariumSupply.com) that I will use for this project. I do not anticipate using riparium trellis rafts in this situation. Many of the best riparium plants (e.g., Pilea, Anubias, Fittonia and others) can grow very well as riparium midground plants planted directly on trellis rafts and with their roots suspended in the water, but I do not know of any brackish water species likely to grow well in this way. Most of the familiar mangrove species grow best in nutrient-rich substrates and are thus better suited for planting the riparium planters with plant media.

I will probably paint the back pane of aquarium glass a black or dark blue color. When hung against a dark aquarium surface the riparium planters become inconspicuous and hard to spot in the riparium planted layout. As the plants grow their leaves, stems and roots will further obscure the planters and create a natural view in the display.

Conclusion

I am already having having a lot of fun with this project! This will be a unique kind of planted setup and I hope to reveal some insights useful for other hobbyists who might like to keep some of these plants and fish. Please visit AquaBotanic.com/ again for the additional articles in this series. My next entry “Plant selection and growing” will cover these fascinating mangrove plants in more detail and also provide a progress update for the mangrove riparium project.

Visit Devin’s web site: www.RipariumSupply.com