Numerous backwater streams and pools make up a unique environment in the tropical Amazon rainforest. These waters tend to be slow moving, low in oxygen, high in fish diversity and rich in nutrients due to the many plants, leaves and tree roots decaying here. Some of the pools are only temporary as they fill up or evaporate depending upon the rainy season. These waters also tend to be reddish-brown in color, soft, and acidic because of tannins released from the high organic concentration. Dark brown to black gravel is recommended to stimulate the natural substrate. Plenty of driftwood and plants are essential to recreate this niche.