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Under the right conditions, aquarium plants can improve an aquarium's water quality. Healthy aquarium plants absorb nitrogen compounds including nitrite and ammonia from the water. The fact is, keeping plants healthy and happy takes more work than most people realize.
Plants and Nitrogen
Unlike animals, plants can metabolize nitrogen compounds. Plants use them as a building block for organic molecules. So all aquarium plants greedily absorb nitrogen from the water. This improves water quality for fish and invertebrates since nitrite is toxic to aquarium fish.
The Needs of Plants
Aquarium plants need to be healthy to absorb nitrite. Foremost, plants need powerful lighting to thrive. The guideline of using lights with an output of 1.5 to 5 watts of light per gallon of aquarium provides enough light for plants to thrive. Different plants need varying amounts of light to thrive, some needing stronger light, toward the 5-watt end of the range, and others needing less. Research your particular species. Most aquarium plants benefit from adding carbon dioxide to the tank through injectors or liquid supplements. Without these needs met, plants won't be able to absorb nitrogen.
In an aquarium, a process called the nitrogen cycle breaks down most fish waste. In this process, bacteria absorb various nitrogen compounds and convert them into more innocuous substances. Healthy aquarium plants can help this process along by absorbing excess ammonia and nitrite. Speeding aquarium cycling through with aquarium plants is called silent cycling.
Plants Adding Nitrite
Under some circumstances, aquarium plants can actually decrease water quality. If you don't meet the needs of aquarium plants, they'll die or shed leaves. The dead plant material rots; it produces more nitrogen compounds like ammonia and nitrite. So if you don't properly care for you aquarium plants, they can actually lead to serious compromises of water quality. This is why you care for your plants by providing strong light and carbon dioxide.
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