The Central America River Environment consists of the major rivers that flow from rocky lakes in the region. The lakes are high in limestone, thus making the river waters hard and alkaline. As the rivers flow toward the coast, they mix with the acidic waters of heavily vegetated side streams. Eventually, they become brackish due to the back flow of coastal streams, bays and estuaries. A medium grade, tan gravel mixed with sand is recommended to simulate the natural substrate. Round, water smoothed pebbles, driftwood, and plants should also be used to recreate this niche.