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How to Use Root Tabs to Fertilize Aquarium Plants

Is your live aquatic plant not growing or losing leaves, even though you’re giving it plenty of light and liquid fertilizer? Most aquarium plants can absorb nutrients from both the water and the substrate (e.g., gravel, sand, or aquatic soil), but some species prefer one method over the other. If your plant is a “root feeder” that favors consuming from its roots, then we need to give it a nutrient-rich substrate or ground-based fertilizers called root tabs.

What Are Root Tabs?

Root tabs are dissolvable tablets or capsules that contain plant fertilizer. At Aquarium Co-Op, we recommend our Easy Root Tabs that are made with mineralized top soil and red clay containing essential plant nutrients, such as:

  • Magnesium
  • Nitrate
  • Phosphate
  • Potassium
  • Manganese
  • Zinc
  • Molybdenum
  • Iron
Easy Root Tabs from Aquarium Co-Op

Easy Root Tabs come in green fertilizer capsules that are safe for fish even if they dissolve in the water.

Are root tabs safe for fish, shrimp, and snails? Yes, our brand of root tabs is safe for all animals. The reason is because we use actual soil in our root tabs that is nontoxic if the nutrients get released into the water column. Some people try to save money by making their own DIY root tabs or using fertilizers meant for houseplants and vegetables, but those terrestrial products can cause dangerous ammonia spikes in the water that may kill your fish and invertebrates.

Which Aquarium Plants Need Root Tabs?

Cryptocoryne plants (or crypts), sword plants, bulb plants, carpeting plants, and plants that produce runners all tend to feed from the substrate and will greatly benefit from root tabs. Stem plants like bacopa and moneywort can absorb fertilizer from the water or ground, but they seem to prefer the former. Plants that don’t need substrate to grow – such as mosses, floating plants, anubias, and java fern – typically do not use root tabs as much.

How to Use Root Tabs

Because root tabs are water soluble, the key is to insert them into the substrate as quickly and deeply as possible. It’s okay if Easy Root Tabs accidentally pop out or get unearthed by your fish because they won’t harm the water quality, but ultimately, we want the root feeders to have access to more nutrients in the ground. Therefore, use planting tweezers or your fingers to push the whole root tab to the bottom of the substrate. (Do not remove the fertilizer from the capsule or else it will dissolve in the water column.)

tweezers in planted aquarium

Plunge the root tab as deeply as possible into the substrate, preferably underneath the roots of plants.

How many root tabs should you use? Place one tab approximately every 5-6 inches (12-15 cm) in a grid so that they cover the entire substrate. If your fish tank is very densely planted, you may need to add root tabs every 4 inches (10 cm) or closer. Ideally, the root tabs should be inserted directly underneath or near the roots of your plants. In fact, larger plants like Amazon swords may need multiple root tabs placed in a circle around their base to keep them well fed.

How do I get the root tabs to stop floating? There is air inside the root tab capsule that causes it to float. To make it sink, poke a hole in one end of the capsule using a pushpin and then squeeze the root tab once it's underwater. Air bubbles will escape through the hole, and your root tab will stay grounded.

How Often Should You Add More Root Tabs?

Nutrients get used up over time (even if you’re using a nutrient-rich substrate) and therefore must be regularly replenished. To maintain healthy growth, we recommend adding more root tabs about once a month to continually build the nutrient base in the ground, especially if you are using an inert substrate like aquarium gravel or sand that doesn’t contain any nutrients on its own. Also, remember that as plants grow bigger, they will require more root tabs. A baby Amazon sword that is newly planted may only need 1 root tab every six weeks, but three months later, that same plant may need six tabs per month to sustain it.

To determine whether or not your plants have consumed all the available fertilizer in the substrate, look closely for signs of nutrient deficiencies. These symptoms can include lack of growth, yellowing and browning, or melting leaves (after the plant was growing well previously). For more information on providing proper plant nutrients, read the full article linked below. Good luck with your planted aquarium and enjoy nature daily.

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