How to care for aquarium plants

Why plants

Live plants do more than look nice. They take up nitrate and other nutrients that would otherwise feed algae, they give shelter to fish that are scared or being chased, and many fish lay their eggs on them. A tank full of healthy, growing plants is often more stable than one without. The Norwegian Food Safety Authority (Mattilsynet) recommends live plants over artificial ones.

Light, nutrients and CO₂

Plants use light to make sugar from CO₂ and water, and they need nutrients to grow. Think of it as a triangle: light, nutrients and CO₂. Whichever one is in shortest supply decides how fast your plants grow.

The most common problem is too much light compared with the rest. The plants can't use all that light, so the algae get it instead. More on that in Lighting: how long and how bright and Algae: which kind and what to do.

Low tech and high tech

Aquarists often talk about two ways of keeping plants:

• Low tech: moderate light, a little fertilizer, and no added CO₂. Plants grow more slowly, but the tank is easier to keep in balance and more forgiving. This suits most people, and beginners in particular.
• High tech: strong light, regular fertilizing and CO₂ from a cylinder. Plants grow fast and dense, and demanding species thrive. But it takes more work and attention, and mistakes quickly lead to algae.

There's no reason to start out high tech. Instead, pick plants that thrive with what you have. You'll find plenty of good choices in Easy plants for beginners.

Nutrients

Fish give plants some nutrients through their waste, but rarely enough of everything. Plants need:

• Macronutrients, especially nitrogen, phosphorus and potassium, in larger amounts.
• Micronutrients, especially iron, in small amounts.

There are two ways to provide them:

• Liquid fertilizer in the water, which suits plants that feed through their leaves, such as java fern, anubias, mosses and floating plants.
• Root tabs or a nutrient-rich substrate at the roots, which suits plants with large root systems, such as cryptocorynes, Amazon swords and vallisneria.

Start with less than the manufacturer recommends, and increase it if the plants show signs of deficiency. Too much fertilizer leads to algae.

What the leaves tell you

The leaves often show what your plants are missing. The hobby doesn't fully agree on what every sign means, but some are common:

• Old leaves turning yellow while new ones stay green: often too little nitrogen or potassium.
• New leaves that are yellow or pale with green veins: often too little iron.
• Small holes or dead spots in older leaves, especially on larger plants: often too little potassium.
• Long, thin stems with wide gaps between the leaves: too little light.
• Leaves rotting right after planting: often just the plant adjusting. Many plants are grown above water at the nursery and shed their leaves before growing new ones underwater. Cryptocorynes are known for this.

Planting and care

• Rhizome plants such as anubias and java fern should not be buried. The thick stem rots in the substrate. Tie them to a rock or a piece of driftwood instead.
• Stem plants go into the substrate one stem at a time, not in a bunch.
• Remove the rock wool and pot from plants you buy, and rinse the roots.
• Trim dead, yellow and damaged leaves so they don't rot in the water.
• Top stem plants that reach the surface, and replant the tops.

When nothing grows

If your plants stall or get worse, go through the triangle: is there enough light, are they getting nutrients, and are algae taking over? Change one thing at a time and give it a couple of weeks.

The app shows how much light each plant needs and how fast it grows.