• Species: Scleromystax kronei

  • Species: Dicrossus(Crenicara) filamentosa

  • Species: Neon Tetra

  • Species: Vallisneria

  • Species: Xiphophorus

  • Species: Ameca splendens

  • Species: Xenotoca eiseni

  • Species: Etroplus canarensis

  • Species: Cryptocoryne

  • Species: Parambassis ranga

  • Species: http://www.smithsaquarium.com.au/

  • Species: Etroplus maculatus

  • Species: Etroplus suratensis

  • Species: Schistura balteata

Biotope Aquaria

16 March 2018


The idea of a biotope aquarium is to try and recreate specific places and environments in as authentic a way as possible. You may want to do this simply for the challenge, but often the fish species being kept need a particular set of environmental conditions that is otherwise hard to provide in a standard community tank. So while a biotope aquarium can seem confining in some ways, it's also a great way to keep the more demanding fish species successfully.

In this article we're going to review some of the more interesting biotope aquaria, and offer up some suggestions of species that might be maintained in them. Bear in mind that many of the more unusual tropical fish are wild-caught, and may be available only at certain times of the year. Your local retailer should be able to provide some assistance in this regard, perhaps by making a special order with their wholesaler, so it's well worth having a discussion with your retailer if a particular species you want isn't in stock. Alternatively, you can try mail-ordering your fish directly from Wildwoods, one of England's most highly regarded suppliers of unusual fish species. You can look over their catalogue on the TF2YD page elsewhere on this site.

Amazonian Flooded Forest

South American tropical fish such as Neons tetra, Corydoras catfish and Angelfish are staples of the hobby, available pretty much anywhere tropical fish are sold. But it's much less common for people to actually create an authentic Amazonian biotope aquarium. What makes the Amazon River so interesting is its strongly seasonal nature, including a distinctive flooding season when the river effectively bursts its banks, submerging huge areas of the tropical rainforest.

Recreating the flooded forest requires the aquarist to imagine a habitat dominated not by rocks or aquatic plants, but with the roots and trunks of rainforest trees. These could be represented using pieces of bogwood arranged vertically, or their artificial equivalents, some of which look very realistic. Rather than gravel, leaf litter would provide the most authentic substrate. Many shops sell dried Indian almond leaves for this, but some aquarists use clean oak and beech leaves for the same purpose. These could be scattered onto a thin layer of either lime-free sand (such as smooth silver sand) or a thin layer of peat or even coconut fibre. Filtration is important, of course, but the water flow should be steady but sluggish rather than turbulent. Air-powered sponges are probably the ideal, but a canister filter fitted with a spray-bar could work well too.

Over time the roots, leaves and peat will help soften and acidify the water, though this effect will be minimal if you start with very hard water. On the other hand, if your water is already quite soft, you might need to use a pH buffer to 'fix' the pH around 7 or 6.5, depending on the types of fish you are keeping. While many of the Amazonian species appreciate very soft and even quite acidic water, the bacteria that perform biological filtration are not happy in acidic conditions, and there's no real advantage to keeping the majority of soft water species below pH 6.5. If you aim for around 2-10 degrees dH, pH 6.5-7, you should find most South American species do very well. Similarly, a temperature range between 22-25C will suit most of the tetras and catfish very well, with only a few fish species, notably Ram cichlids and Discus, needing higher temperatures.

Besides Angelfish, tetras and Corydoras catfish, the flooded forest biotope is perfect for a variety of tropical fish that don't usually do well in community tanks. This includes things like Checkerboard cichlids (Crenicara and Dicrossus spp.) as well as many of the more sensitive Apistogramma.

Central American highland stream

While Central American livebearers are extremely popular among aquarists, they are only rarely kept in truly authentic settings. That's a shame, because their natural environment can be quite easy to recreate, even in quite small tanks. The main thing to remember about this part of the world is that it is dominated by limestone geology, resulting in a network of streams, caves and the famous cenotes that look rather like natural reservoirs. Below the waterline, what you mostly see are open areas of rock and sand, with relatively few thickets of truly aquatic plants. Instead, herbivorous fish such as the livebearers are adapted to graze on algae, which they rasp off submerged rocks with their specially adapted mouthparts. Some livebearers, such as Platies and Guppies, prefer sluggish habitats such as ponds and ditches, but others, like Swordtails, are inhabitants of fast-flowing streams, and it's that habitat we're interested in here.

So the basic set-up for a highland stream aquarium would involve the use of waterworn cobblestones, sand or gravel for the substrate, a few pieces of driftwood for variety, and possibly one or two bunches of plants, such as Vallisneria, adapted to fast-flowing currents and native to the area. A canister filter, either internal or external, could be used to provide the brisk water current and high oxygen levels these fish will need to do well.

In terms of water chemistry, Central American livebearers generally prefer hard rather than soft water: 10-25 degrees dH, pH 7-8, will be fine. Most of the highland stream livebearers prefer cooler conditions, 22-24 C being ideal for the poeciliids in particular, while some of the goodeids may even do better in an unheated aquarium at room temperature (i.e., around 18-22 C).

The classic stream-dwelling poeciliids are the Swordtails, of which Xiphophorus hellerii is the best known. Other species include Xiphophorus comma and Xiphophorus alvarezi. These streamlined livebearers are often not at their best in standard community tanks, but given plenty of swimming room and moderate water currents they are much more rewarding. Avoid mixing different species though, otherwise hybridisation is likely. Goodeids are a less familiar, but equally rewarding, group of livebearers. Because a few species are a bit nippy, while others require quite specific conditions to do well, they are not considered good community fish on the whole. But the two commonest species, Ameca splendens and Xenotoca eiseni, are very attractive and well worth keeping, and occasionally you'll see the shyer, more difficult species, including various Ilyodon species, in stock from time to time.

South Asian coastal stream

The southern coast of India has become quite a popular holiday destination over the last few years, particularly Goa and Kerala. Dotted along the coastline are numerous lagoons and coastal streams, wherein live the only three cichlids native to South Asia, the three Etroplus species commonly called Chromides or Pearlspots by aquarium hobbyists. Alongside these cichlids live a range of gobies, barbs, catfish, and other interesting species that can be used to create an unusual but unquestionably attractive biotope aquarium.

The typical South Asian coastal stream environment is dominated by waterworn boulders and pieces of waterlogged driftwood, both of which will help to divide the tank up into smaller patches that the cichlids can use to define their territories. Lime-free sand should be used for the substrate, smooth silica sand being ideal. Plants native to the area can be used, such as Hygrophila and Cryptocoryne species, but these are strictly optional, and may need to be omitted if herbivorous fish are being maintained. Water chemistry needs to be moderately hard and slightly basic, around 10-15 degrees dH, pH 7.5 being ideal. Some of the species found in this area prefer or require slightly brackish water, in which case 3-4 grammes of marine salt mix should be added to each litre of water, resulting in a specific gravity of around 1.001-1.002. This won't be enough to upset hardy plant species, including Hygrophila polysperma and Cryptocoryne wendtii.

If you're focusing on the strictly freshwater end of the range, good community tank choices include Indian Glassfish (Parambassis ranga), Striped Dwarf Catfish (Mystus vittatus), Filament Barbs (Dawkinsia filamentosa) and of course the beautiful Canara Pearlspot (Etroplus canarensis), this latter species easily holding its own in a well-maintained single-species set-up as well.

If you're adding a bit of salt, you could try mixing Orange and Green Chromides respectively (Etroplus maculatus and Etroplus suratensis respectively). The first of these is a dwarf species, no more than 8 cm in length when fully grown, but the second is much bigger and more overtly herbivorous, ruling it out from both small and planted tanks. But the two species seem to have a symbiosis of sorts in the wild, and coexist well, given enough space, Green Chromides reaching an adult length of around 25-30 cm in captivity. These two cichlids might also be combined with low-end brackish water species from South Asia. In the case of the Orange Chromide, this might include Indian Glassfish and Knight Gobies (Stigmatogobius sadanundio). Green Chromides tolerate moderately brackish water well, up to a specific gravity of 1.010, and may be mixed with things like Archerfish, Scats and Monos without problems.

Do note that Etroplus are gregarious and hierarchical. They work best in large groups, six or more specimens, whereas smaller groups may result in weaker specimens being bullied by the dominant fish.

East Asian Hillstream

Although East Asian fish have been imported on and off for years, consistent deliveries of species from China and Taiwan in particular is a relatively recent phenomenon. There's a wide range of cyprinids, loaches and gobies native to the upland streams of East Asia, many of which make interesting and colourful aquarium fish. The big problem for casual aquarists is that these fish are adapted to cool, fast-flowing waters and do not do well in generic community tanks. Instead, they must be provided with a clean tank equipped with robust filtration that ensures good water quality and plenty of oxygen.

The chief concern with this type of biotope tank is water circulation. The easiest way to handle this is by using internal or external canister filters, perhaps supplemented with powerheads or airstones. The important thing is that water circulation rates are high: 10-12 times the volume of the tank per hour. So if you're creating this type of biotope using a 100-litre aquarium, you'd need a filter (or multiple filters combined) with a turnover rate of 1000 to 1200 litres per hour. The other main consideration is temperature. Depending on the species being kept, around 18-22 degrees C is typical, though some species may require slightly warmer or cooler water to do well, so check before combining different species in the same aquarium. Water chemistry is of secondary importance, though neutral, slightly soft to moderately hard water is probably ideal.

The two key groups of fish that only do well in hillstream biotopes are the Balitoridae and the Nemacheilidae. Numerous species of both are imported, the most common of which are balitorids often sold as Hong Kong Plecos, usually species of Sewellia, Pseudogastromyzon and Gastromyzon. These resemble a cross between a catfish and a flounder, having flat bodies and sucker-like fins that help them hold onto rocks even in the strongest currents. With a maximum length of around 6-8 cm, and often rather beautiful green and black speckled bodies, these fish have been popular oddballs for years, but few live long in generic aquaria, so if you want to keep them, a biotope is definitely the way to go.

Among the nemacheilid loaches, species of Schistura are probably the most often seen, particularly those sold as Sumo Loaches, which are either Schistura balteata or some closely related, but as yet unidentified, species. Whereas the balitorids are rather harmless algae eaters that do little more than shove each other favoured feeding spots, the nemacheilids tend to be a bit more feisty, so some care has to be taken with regard to stocking these territorial loaches. Each loach has its own hiding place, but since this biotope calls for plenty of waterworn rocks and bogwood, providing such caves and burrows shouldn't be hard.