Mastering Freshwater Aquarium Ecosystems
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Biotopes (Cont.)

In the aquarium Central American cichlids are often kept with little or no aquatic plants. They can be kept in aquariums with floating water sprite (Ceratopteris thalictroides) and other floating plants to help reduce nitrate accumulation. Since many Central American cichlids dig in the substrate it may be difficult to keep rooted plants. Potting plants often will work with these cichlids.

Central American cichlids tanks are prime candidates for incorporating a refugium or hydroponics filtration in the ecosystem. Without out a refugium or hydroponics filtration, nitrate concentration can increase quickly, requiring frequent (weekly) 75% or greater water changes to avoid hole in the head symptom.


Amazon fish we see in the hobby are primarily soft acidic water fish. Hobbyist that keep fish from the Amazon often have wood as decoration. A tea colored water is common in Amazon biotope aquariums. Fish that are often kept in Amazonia biotope are discus (Symphysodon  sp.), angelfish (Pterophyllum scalare), Apistogramma sp. (dwarf cichlids), cardinal tetras (Paracheirodon axelrodi), rummy-nose tetras (Hemigrammus rhodostomus), neon tetras (Paracheirodon innesi), plecostomus, and Corydoras catfish.

While many of the fish from the Amazon region will adapt to hard alkaline water, for breeding, soft, low pH water may be required for some species. Many of the fish that come from the Amazon will have much higher hatch rates if the water is soft and acidic. Most Amazon fish prefer a pH between 4.0 to 7.2.

Amazon sword plants (Echinodorus bleheri) make an excellent plant for an Amazon biotope aquarium as they do well in soft acidic water. Amazon sword leaves are often used as a spawning site by discus and angelfish.

Wood is a common decoration in Amazon biotope aquariums. If you are keeping discus or angelfish, providing a few pieces of vertical standing wood will be appreciated, and often used as a spawning site. Coconut half shell with a hole drilled in the side can provide a natural look and be a preferred spawning site for many Apistogramma sp. dwarf cichlids.

Amazonia Biotope Aquarium

This 90 gallon (342 l) Amazonia biotope aquarium has wood, and Amazon swords (Echinodorus bleheri) as well as a few other species of plants. Fish are discus, tetras, plecos, and Corydoras sp. catfish.

If you maintain a Amazon biotope you must be aware of the affect low pH has on nitrifying bacteria. Ammonium reading is common in low pH systems, due to reduced bacterial populations. When a water change is done on a system with a low pH, ammonium can be converted to ammonia if the pH of the new water is much higher than the aquarium water.

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