When Should I Dose Iron in My Planted Aquarium?

Just as people need certain nutrients to function correctly, aquatic plants require a unique mix of fundamental building blocks to live and grow. Macronutrients (like nitrogen, potassium, and phosphorous) are nutrients that plants consume in large quantities, where as micronutrients (like iron and boron) are nutrients that plants consume in trace amounts. Many all-in-one liquid fertilizers like Easy Green already contain iron (Fe), so when is it necessary to dose additional iron in your planted tank?

Do My Aquarium Plants Need More Iron?

Iron is utilized by plants to produce chlorophyll, a green pigment that helps plants to absorb light and make energy. In general, plants that are fast-growing or need bright lighting use lots of energy. In order to get more energy, they often require supplemental iron to produce an abundance of chlorophyll. Therefore, adding extra iron in your aquarium can result in healthier plant growth and more vivid colors.

Do my aquarium plants have an iron deficiency? An interesting fact about iron is that it cannot freely move from one area of the plant to another area that lacks it. Consequently, if your aquarium is low in iron, the newest leaves on the plant look pale or yellow from insufficient chlorophyll, whereas the old leaves still retain their bright colors.

Plants that lack iron may display yellowing or paleness on their newest leaves with leaf veins that remain darker in color. 

Do red plants need iron? Iron primarily helps to create green chlorophyll pigment and not red pigment. However, red plants like scarlet temple or Ammannia gracilis can benefit from extra iron because many of them are also high light plants that consume more nutrients in general. Red-leafed plants contain large amounts of red pigment and smaller amounts of green chlorophyll, and scientists are looking into the purpose of these red pigments and why red plants become more vibrant in bright sunlight. Under intense lighting, the red pigment may serve to protect leaves from excess light energy, and the amounts of green pigment may be decreased since not as much chlorophyll is needed to collect light photons. For the aquarium hobby, we recommend a combination of high light, carbon dioxide (CO₂) injection, and good nutrient dosing (including iron) to enhance the redness of your plants.

With certain red plants, the topmost leaves closest to the light may turn pink, red, or even purple, whereas the lower leaves in the shade stay green.

Bottom line: if your planted aquarium isn’t displaying nutrient deficiencies and you aren’t trying to grow high light plants, you probably don’t need to add any extra iron beyond what comes in Easy Green fertilizer. You also don’t require supplemental iron If you are using well water or iron-enriched substrate that already contains excess iron. However, if your tank has greater iron demands than what is currently being provided, keep reading.

How Often Should I Add Iron to My Aquarium?

Easy Iron is our iron supplement for enhanced plant growth that is completely safe for aquarium fish, shrimp, and snails. It contains a highly concentrated blend of iron derived from ferrous gluconate, iron DTPA, and iron EDTA. Plus, it comes in two sizes with easy-to-use dispensers for quick dosing.

• The 500 ml (16.9 oz) bottle treats 5,000 gallons total and has a pump head on top. Dose 1 pump (1 ml) per 10 gallons of water to add 0.26 ppm of iron.
• The 120 ml (4 oz) bottle treats 1,200 gallons total and has a dropper cap on top. Dose 2 drops per 1 gallon of water to add 0.26 ppm of iron.

Iron is utilized quite rapidly in aquariums, so we recommend dosing 1-3 times a week as desired. When in doubt, start with a low dosage and slowly increase after two weeks. People have reported an increase in filamentous or hair algae when an excessive amount of iron is used. Some planted tank articles recommend aiming for a range of 0.1-0.5 ppm iron in your aquarium water.

Aquarium Co-Op Easy Iron

Why doesn’t Easy Green contain more iron? Easy Green fertilizer does already contain iron, but in trace amounts that are appropriate for most planted aquariums. High concentrations of iron do not mix well with other plant nutrients and minerals, so we created Easy Iron as a separate product that can be added when necessary.

If you are having problems with your live aquatic plants and they do not appear to be caused by a lack of iron, check out our full article that describes other plant nutrient deficiencies to see if any of the symptoms match. Good luck with your planted tank, and enjoy nature daily.