Plants aren't just eye candy for your aquarium fish. Depending on the circumstances, your plants can raise or lower nitrite levels. Nitrite is toxic to aquarium fish, so understanding what controls nitrite is vital. If you take good care of your plants, you can use them to alter nitrite levels.
Plants Can Lower Nitrite
In a perfect world, aquarium plants can reduce the nitrite level of an aquarium. Aquarium plants will absorb nitrite from the water, either through their leaves or roots, and use it as a nutrient. Unlike most animals, plants can use nitrite as a building block for more useful -- and less toxic -- nitrogen compounds like proteins and nucleotides. However, this only works if the plants are healthy and happy.
Plants Can Also Raise Nitrite
Under the wrong conditions, aquarium plants can also raise nitrite levels. Aquarium plants require more care than many people realize, and poor care can lead to increases in the nitrite level. A dead or dying plant can decay, which produces ammonia. Ammonia turns into nitrite in an aquarium, and both compounds are toxic to aquarium organisms. Additionally, some aquarium plants need pruning, since old growth tends to die off. Any decaying plant material can produce toxic nitrogen compounds like nitrite and ammonia.
Improving Plant Health
In order to get plants to absorb nitrite, you have to provide them with ideal conditions. Research your specific species of aquarium plants, as many have different requirements in terms of lighting and temperature. Most species need more powerful lighting than a fish-only tank. Use at least 5 watts per gallon, and light the tank for 10 to 12 hours per day. Plants also thrive when you add fertilizers rich in potassium and trace minerals to the tanks. Lastly, most aquarium plants benefit from the addition of carbon dioxide. You can find fertilizers and carbon dioxide products at many pet shops.
If you're worried about nitrite levels, try a few steps to improve the situation. First, most pet shops sell test kits for nitrite. Use a kit to test your water every two to four weeks. Test more often if you've just added new fish or see signs of distress in your scaly buddies. Additionally, monthly water changes remove nitrite from the tank. Lastly, keep an eye out for extra food or bits of dead plants in the water. These items rot and add nitrite to the water.