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 Biotopes - Part 1

Biotopes, Part 1

by Alesia Benedict


One of the "buzz terms" you'll hear in the hobby is “biotope tank”-- but what exactly IS a “biotope tank?”  A biotope tank is defined as an aquarium in which the inhabitants are all from a specific region, and found together naturally in the wild. Probably the most well known 'tope is the Amazonian tank, but I thought we'd first travel to other parts of the globe and start with some of the lesser-known, but highly interesting ones: the West African River Rapids, the Southeast Asia Back-Waters, and the Southeast Asian River.



Based on a portion of the Zaire River, which encompasses the longest section of whitewater rapids in the world. If you like waterfalls, this might be the tank for you. The Zaire River itself is nearly 2,800 miles long, contains a drainage area which covers 1.5 million square miles, and is known for having more than 30 waterfalls amongst its rapids. Only very hardy plants can be found here, as they must be able to handle the tumultuous water swirls. To simulate the rapid water flow, choose a good power filter for the tank. If waterfalls are your "thing," and if you don't mind the noise (and understand that you will lose CO2), you can even fill the water level to only 75%, thus providing a small waterfall right there in your tank!.

Tank Specifications

Ideally, the water temperature should be in the upper 70's, with a pH between 7 and 7.5, and a water hardness of moderately hard. Depending on the depth of the tank, lighting might be as easy as a single or double strip fixture. And while you can use nearly any sized tank, because of the need to simulate the many river boulders, at 36x18x15, a 40 gallon breeder tank is a near perfect size for aquascaping this biotope.

Plants for the Tank

In nature, most plants would easily be uprooted and swept away. To compensate for the constant and rapid water flow, plants of this region root themselves amongst the river's bare boulders and grow from the crevices between the rocks.  Hence, it’s no surprise that the popular plant family known as Anubias come from this region. With such splendid variations as the Congo Anubias (Anubias congensis), the Anubias lanceolata, and the Dwarf Anubias (Anubias nana), we can decorate the tank with an array of beauty and contrast. Another native plant we can use is one that also roots on rocks; Bolbitis heudeloti, a real stunner of a plant with its deep, dark green color.


To the uninformed observer, the substrate will appear to be just silver sand and big rocks. However, to prevent shifting and such, first spread a generous portion of gravel as the first layer, and arrange some large, smooth rocks towards the back of the aquarium. The gravel will hold the rocks in place. These rocks, vital to the aquascape, simulate the many boulders "shaped" by the Zaire River's rapids, so be sure all the rocks are smooth and round. Towards the front of the tank, add some smaller rocks and big pebbles. Now comes the silver sand -- cover the gravel completely with just your rocks and big pebbles showing, then add the foliage. Tuck the plants between the rocks and into the gravel.  Now, slowly add dechlorinated water, being careful to disturb the sand as little as possible (Note: pouring water onto the back glass or using an inverted saucer aids greatly in reducing substrate disruption).


Phenacogrammus interruptus is one of many fish suitable for a Zaire river rapid biotope.  Photo by Robert Fenner.

Rapid-water Fish

At the appropriate time you can add your fish. Fish found in the Zaire River rapids include African Red-Eyed Tetras (Arnoldichthys spiolpterus; Banded African Tetras (Distichodus sexfascatus); African Glass Catfishes (Eutropiellus debauwi); Butterfly cichlids (Hemichromis thomasi); the very beautiful Congo Tetras (Phenacogrammus interruptus); the quirky Blockhead Cichlids (Steatocranus casuarius); the peculiar Upside-down Catfishes (Synodontis nigriventris); and a number of other fish (in fact, more than 60 species).

Interesting a tank though it is, if you find yourself getting a little queasy from all that talk about whitewater rapids, perhaps instead you’ll prefer our next biotope, the slow-moving waters of Southeast Asia.



The back-waters as they are called, are both slow moving and dense with plants and organic matter. The waters contain few minerals save for one: they are iron-rich. For this reason, the floor is often a deep red in color and the waters themselves are shallow, low in oxygen, and crammed with insects on which the fish eat. Perhaps the most well-known of the fish found in this region is the Betta (sometimes - ugh! - called the Siamese fighting fish), which inhabits the waters of the irrigation streams for the region's paddyfields. I really like this biotope because it is a fairly easy one to build and maintain, and when properly set up, planted, and stocked with fish, it serves as a living pallete of color and movement.

Tank Specifications

Size doesn't matter too much here, so select a tank that will work for you. To keep the lighting simple, however, make sure you don't select a tank that's too deep. A 20-long or a standard 29 gallon tank with either a double or a "triple" strip light (one single plus one double) would be wonderful choices. Water temperature should be in the mid 70's to just about 80 degrees, and the pH should be 6-7. Water hardness should be moderate, and not allowed to rise too high.

Plants for the Tank

 Two native plants to this region are the Giant Hygrophila (Nomaphila stricta), a quick growing bushy stem plant that, if left uncovered, will grow right out of the top of your tank! A beautiful emerald shade of green, this easy plant makes a very dramatic appearance in the tank and is sure to "wow" both you and your friends/family/guests.  The other, the Bamboo Plant (Blyxa japonica), is an elegant, long-leafed plant that seems to dance in the water  with just the slightest current.


While some readers may balk at me saying this is a fairly easy tank to maintain since we're planting Bamboo Plants. However, by using the red version of Flourite, your substrate will not only resemble the region's streambeds in color, but it will also be iron-rich, something to which these plants will respond with rapid and sustained growth. Before adding your fish, make sure the plants' roots have taken a firm hold, otherwise you'll constantly have to replant the sprigs because the roots stay fairly shallow. If you aren't as patient as I am, and don't want to wait two weeks to add your fish, you can use plant weights to aid in their anchoring.  Now add some large pebbles in close proximity to one another so that little gaps appear, which, along with the tall plants, will offer some hiding places for the more timid fish. It's easiest if you fill half the tank with water before planting -- once you've finished planting, you can fill the rest of the tank. Remember to use dechlorinated water and try not to disrupt the substrate.

2576_Danio_rerioZebra_Danios3.tif.jpg 2606_Botia_macracanthaAQ3in.tif.jpg

Zebra Danios and Clown Loaches are just two of the many commonly available fishes that fit neatly into a South East Asia Backwater biotope.  The wide availability of fish from this region make it a fairly easy biotope to duplicate.  Photos by Robert Fenner.

Back-Water Fish

To compensate for the low oxygen levels within the water, many species of Labyrinth Fish are found in these waters, including various Gouramis (Colisas) and to some degree, Paradise Fish (Macropodus opercularis) -- though it prefers cool water.  Other choices include Bettas, Clown Loaches (Botia macracantha), and Tiger Barbs (Barbus tetrazona) -- and while The Complete Aquarium by Peter Scott (a good read for more information on various biotopes) states that it is OK to put these fish together, I wouldn't want to subject a Betta to the tiger Barbs' fetish for fin nipping. However, one of my favorite tanks that I have is a 29 gallon aquarium housing various plants (I never can seem to adhere to a 100% pure biotope tank), a cave, and just tiger barbs and clown loaches.  It is visually dynamic with a mass of yellow and black stripes constantly on the move, and the coloration of these fishes against the green of the plants is nothing less than spectacular.

Other interesting possibilities for a back-water tank include those cool-looking Glass Catfish (Kryptopterus bicirrhus), the striking Red-Tailed Black Shark (Labeo bicolor), the quick- swimming Zebra Danio (Brachydanio rerio), and a shoal of Asian Shark Catfishes (Pangasius sutchi).

If you've read thus far but you're thinking, "HEY!  How come she hasn't mentioned Crypts, those plants are from Asia?", it's because while they are indeed found in Asia, they are not among the back-water plants, but instead, hail from our third biotope, the Southeast Asian River.



At one time, mainland Asia and the Asiatic islands (Sumatra, Borneo and Java) were all joined by land, and one great river system flowed through the whole area. Our biotope tank is based on the lower reaches of an Asiatic island river. I think it’s quite interesting, as these lowland sections may contain salt, and we'll talk about that in the next section.

Tank Specifications

Once again, tank size is not critical so choose one that best suits your needs, taking into consideration the adult sized fish you want. Water temperate should hover at 75 degrees, with a pH of 7.0 to 7.5 and keep the water moderately hard. Adding a bit of aquarium salt to the water (1/2 to 1 teaspoon per gallon) will do the fish good while not harming any of the plants. Since you will not need too much lighting for the tank, a single or double strip light will be fine. Your filter of choice should provide a steady flow, but concurrently not too strong. Water movement is good, turbulence is not.

Plants for the Tank

Yea, here's where the very popular Crypts can be used! Cryptocorynes are wonderful plants and within this family exist many different species, each with its own “look”. Crypts, however, are also a temperamental plant -- I won't say they are “difficult”, but they aren't “easy”, either.  They are ... well, moody!  I have some variation or another in all my planted show tanks, and most of them, most of the time, do great.  But then, for no apparent reason, one of them will start to fail. Just like that. While they can be moved, they aren't too fond of it, and when I do so or dig one up to separate it, it takes a bit of time to recover. Crypts also hate new tanks!  If you are setting up a brand new tank, wait until a few months go by before adding them, as they favor more conditioned water. Then there's the famous "Crypt Rot" or "Crypt Meltdown". But wait, I digress here....

Plants that can be used for this tank include varieties of Cryptocorynes as well as Vallisneria, Hairgrass, and Crinum thaianum. This plant's popular name (“Onion Plant”) describes it perfectly, as it sprouts and grows from a bulb which should be only partially buried into the substrate. If you allow this plant to grow out of the tank and out of the water, it may produce white flowers. The giant Vallis (Vallisneria gigantea) will produce runners across the bottom of the tank, nicely filling in gaps. Hairgrass (Eleocharis acicularis) can also be planted, as well as Japanese Cress (Cardamine lyrata).


I think this tank is really fun to set up, because it is designed to resemble an area in the river surrounding a large tree root. It also breaks with the traditional way of planting a tank, with taller plants in the back, and small, bushy ones in the front.  This is because, in the natural environment we are attempting to replicate, the tall plants grow in the center of the river (hence, the front and center of the tank), and smaller plants line the banks. Using Onion Plants and Vallisneria in the front and center, for example, with their thin, long leaves reaching toward the top of the aquarium, provides us with plenty of "sight space" to plant Hairgrass and Crypts.  I define "sight space" as being able to see these smaller plants through the long tresses of the onion plants and Vals.

Now, add some gravel to create a bank, building up a back corner to resemble a bend and terracing it (to make it stay in place) with small rocks and big pebbles. The base of the tank should be littered with small rocks and big pebbles, and trust me, you'll need more of them then you think you will!  Next, cover the gravel, pebbles, and rest of the tank with some silver sand.  This mimics the look of sand deposited naturally in the river, so brush off the sand that collects on very top of the rocks. Next, position a large piece of bogwood or sinking driftwood so that it resembles an exposed root in the riverbed. Place some pebbles at the base of the wood and across the entire tank. Next, plant your plants in the pattern we discussed above.

2565_Puntius_conchoniusRosyBarbsAQ2.tif.jpg 2578_Danio_aequipinnatusGiant_Danios.tif.jpg

Rosy Barbs (left) and Giant Danios (right) both make great South East Asian river biotope fish.  Photos by Robert Fenner.

Southeast Asian River Fish

Along with some of the fish from the previous biotope (Clown Loach, Red-Tailed Black Shark, Betta), you can also add a shoal of Coolie Loaches (Acanthophthalmus kuhli), or choose from many other popular fishes, such as Rosy Barbs (Barbus conchonius), Pearl or Giant Danios (Brachydanio albolineatus and Danio aequipnnatus), or a shoal of Scissortails (Rasbora trilineata). As always, keep in mind the size of the adult fish vs. the size tank you have selected, remembering never to overstock!

One last note: in using rocks, pebbles, bogwood, etc., make certain all items are completely 100% aquarium safe!

Next Time

Next time we'll be traveling to a Papua New Guinea Sandy River, a Central American Coastal Stream, and finally heading back to Southeast Asia to discuss a tank I intend to someday set up, a brackish water estuary. Make sure you've got your passports ready!

Freshwater Biotopes on WWM

Related FAQs: Freshwater BiotopesFreshwater Community,

Related Articles: Biotopic Set-Ups, The Subtropical Aquarium; A cooler kind of fishkeeping by Neale Monks, Aquascaping for Beginners; Twenty Tips for Realistic Aquaria by Neale Monks, Aquascaping Adventures in Aquascaping by Timothy S. Gross  



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