Aquarium Plant Fertilizers

Healthy plant growth in saltwater and freshwater aquariums depends on CO2, iron, light, substrates and a nourishing fertilizer that will not harm the fish. Properly fertilized plants will grow lush and provide fish something to graze on and swim among. It is important to consider several factors when deciding what types of fertilizer to buy, including how heavily planted the aquarium is. An aquarium with only one or two live plants likely does not need any fertilizer, as the plants can obtain the nutrients they need from the water, rocks and fish waste.

  1. Fertilizers for Freshwater Plants

    • Live aquarium plants can thrive with the proper fertilizer.

      Aquarium plants absorb nutrients through the roots and leaves, as opposed to above-ground plants which usually only take in nutrients through the roots. To thrive, the water plants need a mix of nutrients, which can be delivered through fertilizers: phosphates, calcium, nitrates, potassium, magnesium, sodium, chloride, iron, copper and zinc. Water plants should not be fertilized with the same mixture as above-ground garden plants, as those mixes typically promote algae blooms, which are harmful in aquariums. Fertilizers specifically for aquarium plants can be found at pet shops, some garden supply centers, and through many retailers online.

    Types of Freshwater Fertilizers

    • Fertilizers for aquarium plants come in liquids and tablet forms.

      Fertilizers are sold in dry or liquid forms. Liquids work best for floating plants and "unrooted" varieties, and should be timed with water changes. Dry fertilizers, typically in tablets, release the ingredients slower and are geared toward plants with root systems. Consult the labels for dosing amounts and frequencies. Optimum fertilizers will have a high iron content.

    Plant Hormones as Fertilizers

    • Saltwater aquarium plants can benefit from fertilizers.

      Some pet stores and online retailers sell pre-packaged hormone solutions for aquarium plants. These are intended to stimulate plant growth and can contain a mix of GA3 (giberellic acid), potassium humate, and IBA (indole-3-butyric acid). Consult the package for dosing information.

    Fertilizers for Marine Aquariums

    • Plants in saltwater aquariums require the same nutrients as their freshwater counterparts. If there are only a few plants in the aquarium, they can get by without store-bought fertilizer, relying on the water and fish waste. However, a heavily planted saltwater, or marine, aquarium, can benefit from supplements added to the substrate, the base material the plant grows on. Consult the labels to determine if the fertilizer is specifically for marine aquariums or can be used with any planted tanks.

    Fertilizing is Only Part of the Routine

    • Healthy plants help beautify an aquarium.

      Fertilizing plants produces good results when used in conjunction with regular water changes, and when using an aquarium with good water circulation that can help mimic the water flow and gentle currents that the plants would have in the wild. Having adequate lights for the plants, a desirable temperature and monitoring the water's pH will help the fertilizer do its job. Testing for water hardness is crucial, as water that is too hard makes it more difficult for the plant to absorb nutrients. Avoid mixing plant types that do well with different temperatures and water hardness.

    Do-It-Yourself Fertilizer

    • Some hobbyists mix their own fertilizer by combining 1 1/2 cups of distilled water, 2 tsp. of potassium sulfate, 1 tsp. of potassium nitrate, 2 1/2 tbsp. of hydrated magnesium sulfate, and 1 tbsp. of a chelated trace elements mix that can be purchased from pet stores. The dose depends on the variety and number of plants, and the size of the aquarium, but usually starts with a few drops for each 10 gallons in the aquarium.