Reasons Why Aquarium Water Turns Green: Quick Fix Guide

Why Does Aquarium Water Turn Green?

It's quite common for aquarium water to turn green, but the reasons behind this phenomenon can vary greatly. Therefore, it's crucial not to rush into frequent water changes, as this can only stress the fish and potentially lead to illness.

The greening of aquarium water typically occurs in two distinct scenarios:

1. Water turns green but remains relatively clear, with a careful observer able to spot floating green algae.

Common Causes:

① Excessive Lighting: Generally, an aquarium should be illuminated for about 8 hours a day. Prolonged exposure to light can promote the growth of planktonic algae and also disrupt the normal rest and metabolism of the fish.

② Overabundance of Organic Matter: Feeding the fish too much food that they can't consume leads to leftover food scraps and fish waste accumulating, which can degrade water quality and cause the water to turn green.

③ Oxygen Deprivation: High fish density, excessive organic matter, and infrequent water changes can lead to oxygen depletion in the aquarium. The decomposition of organic matter produces nitrogenous compounds and carbon dioxide, leading to an overoxygenated state and a proliferation of planktonic algae.

④ Low Water pH: Water with a pH below 6 is more prone to turning green.

2. Water appears yellowishbrown and murky, with a noticeable abundance of brown algae.

Common Causes:

① OverFertilization: Some aquarists frequently fertilize aquatic plants, which can lead to an excess of nitrogen, phosphorus, and potassium. If fertilization is excessive, the plants can't absorb all the nutrients, allowing brown algae to thrive.

② Insufficient Nitrosomonas: A lack of these beneficial bacteria can lead to the accumulation of nitrogenous compounds as organic matter increases, resulting in the production of nitrites. High levels of nitrites can trigger the rapid growth of brown algae.

③ Phosphorus in Feed: The growth of planktonic organisms requires phosphorus, and feeding fish with phosphorusrich food can easily lead to algae blooms.

What Are the Dangers of Green Aquarium Water?

Green water in an aquarium can be catastrophic for the fish, as green and brown algae can also undergo photosynthesis in the presence of light. During the day, they compete with aquatic plants for carbon dioxide and sunlight, and at night, they absorb oxygen from the water, impacting the growth of plants and fish. If algae overgrowth occurs, it can侵占 the living space of plants and fish, consume large amounts of oxygen, and lead to fish gasping for air, which can ultimately result in their death.

Additionally, some algae types are toxic, such as green flagellates, yellow flagellates, and brown flagellates. The presence of large amounts of these algae can cause poisoning in beneficial organisms and fish, leading to fatalities.

Therefore, aquarists should carefully investigate the specific causes of green water in their tanks and take timely action to address them, to prevent any harm to the entire aquarium's inhabitants. For more tips on fishkeeping, check out our article on "The Right Way to Change Aquarium Water" for further reading!