Amazon Pool Biotope

As the Amazonian floodwaters subside, pools of water remain in the ruts and depressions of the forest floor. As the days roll on,  the tropical heat will rapidly evaporate many of these small water bodies. For the unlucky fish that are herded into these smaller pools, death is inevitable. Those fish which find themselves in a larger pool will enjoy a more favorable outcome.

Water bodies which are large enough to last until the next rain season become the model for the Amazon acid pool biotope. The low pH results from the abundance of decaying organic matter produced by shedding leaves and fallen branches. PH readings as low as 4 or 5 are not uncommon. Humic acids and tannins from the wood stain the water brown. Low mineral content of the collected rainwater makes for minimal hardness. The high biological load from the thriving compost bacteria drain the water of oxygen as the vegetation is processed. Summer sunlight can raise the water temperature to 35 degrees where shallow pools have formed below breaks in the tree top canopy.

This harsh scenario would be fatal to many aquatic animals, but the fish of the Amazon have evolved to thrive under such conditions. The pH drop and abundant warmth often triggers fish into breeding behaviour. Such conditions are ideal for developing fry. Young fish can gorge themselves on the banquet of microbial soup. The substrate of mud and leaf litter provides ample hiding opportunities for vulnerable baby fish to retreat within.

The fish that collect in these temporary water bodies are typical of the species associated with the region. Discus cichlids, angelfish, some catfish and many tetras would all be geographically correct choices for the Amazonian acid pool biotope aquarium. These fish are not typically kept at such a low pH and hardness in a domestic setting but can adapt and acclimatize to such a biotope.

When choosing decorations the substrate should be made up of dark coloured gravel to simulate an earthy feel. Leaf litter and mud could be used but the impracticalities make this a rarely used substrate. Bogwood and tree roots make an excellent ornament choice. The leached tannins from such decorations will tinge the water with a brown stain for a realistic touch.

Submerged aquatic plants are often found in Amazon pool conditions and should also be incorporated into the home biotope also. Amazon swords are an obvious choice because of their acid tolerance and geographical correctness. Anubias varieties are welcome inclusions that can bond to and grow upon the included bogwood and tree roots. Floating plants such as Azolla species, salvinia species and water lettuce can be incorporated to simulate dappled light and floating organic matter.

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