How to grow & care for aquarium plants

Lighting

Different plant species have different requirements when it comes to lighting, and researching the species you are interested in is therefore really important. Many aquarists claim that planted aquariums are really difficult to keep, since they purchase plants that look good without putting any effort into learning how these plants should be cared for. It is not hard to understand why these plants rapidly wilt and die in the aquarium, and why the aquarist believes that planted aquariums are “impossible” to keep.

Strength
As a rule of thumb, planted aquariums should get 0.5-1.0 watt of fluorescent light per liter of water. Generally speaking, a 50 liter aquarium with standard dimensions will therefore require 0.5 watts x 50 = 25 watts. This rule has to be modified if you keep really high demanding or low demanding species, if your aquarium is very deep, or if your aquarium is really densely planted.

Incandescent or fluorescent?
Incadenscent lighting is still quite common, especially among beginners. There are many low demanding plant species that will do well with nothing but incandescent lights, but the problem is that incandescent lights tend to become really warm. This will affect the water temperature in your aquarium. Incandescent lights also consume a lot of energy and do not last very long. Investing in fluorescent lights can therefore save you money in the long run.

Color temperatures
When purchasing fluorescent lights from a well stocked lamp store, you may stumble over a wide range of different color temperatures. Different color temperatures are good for different purposes. If you are a novice plant keeper, stick to bluish (white) and yellow (warm) lamps.

Day length
Try to mimic the natural day length in the environment from which your plants hail. Many popular aquarium plants are tropical species and are therefore used to 12 hours of light per day. If you keep temperate species, give them at least 14 hours of light each day during the summer and no more than 10 hours per day during the winter. Keeping the lights on 24/7 will only aid algae growth and may also disturb your fish.

Carbon Dioxide (CO2)

Without carbon dioxide, plants cannot perform photosynthesis, the process where they turn light energy into energy that they can use (sugars). Most plants will do well with the carbon dioxide produced by breathing fish and other animals in the aquarium, but there are of course exceptions. Some aquarists use CO2 injections to promote plant growth. This can produce wonderful results when balanced with sufficient lighting and necessary nutrients. Even plants that would survive without any additional CO2 can start growing much more rapidly when they receive extra CO2. CO2 can come from fermentation or from a gas cylinder filled with liquid CO2. 

Fermentation
Producing CO2 through fermentation is actually quite straightforward and can be carried out even by aquarists on a limited budget.

1. You will need a 1.5-2.0 liter plastic bottle.
2. Poke a hole in the cap and let an airline tube run through it. (The attachment must be airtight.) The airline should ideally have a non-return valve.
3. Fill half of the bottle with water.
4. Shake in ½ cup of sugar and ½ teaspoon of baking yeast.
5. Secure the cap and wait for the fermentation process to start. It should be up and running in no time, just like when you bake a loaf of bread.
6. When gas starts to evaporate through the airline, attach an air stone to the tube and place it in the aquarium.
7. The fermentation process will normally provide the aquarium with plenty of carbon dioxide for at least two weeks. 

Nutrients

Just like terrestrial plants, you aquarium plants need nutrients to survive.

Macro nutrients: Nitrogen, Phosphate, Potassium
Other nutrients: Boron, Iron, Nickel, Zinc

In addition to the elements mentioned above, plants need trace elements of many other elements as well. If you fail to provide your plants with all necessary nutrients, it can lead to stunted growth, yellow leaves or even prove fatal. So, how can nutrients enter the aquarium?

• Nutrients are present in tap water and well water.
• Nutrients are present in fish food (and will therefore also be excreted by fish).
• Nutrients are present in potting soil and aquarium substrate.
• You can purchase special fertilizers intended for aquarium use.

Before you decide on using fertilizers, keep in mind that simply filling your aquarium with a lot of fertilizers will not aid plant growth. Fertilization must always be balanced with light and carbon dioxide. It is also very important to purchase a special aquarium fertilizer, since fertilizers for terrestrial plants contain too much nitrogen which will cause algae growth and injure the fish. 

Substrate

Some aquarium plants must be planted in the substrate or in pots, while others grow attached to rocks, driftwood etcetera. There are also floating plants and plants that can grow in several different fashions. If you want to keep plant species that need a substrate to grow in, ideally chose a substrate where the particles are 1.5-3.0 mm. There are naturally exceptions to this rule, but many plant species can not tolerate finer substrates since their roots cannot handle anaerobic conditions well. When the particles are 1.5 mm or bigger, it is easier for water to circulate which prevents clogging.

When it comes to substrate depth, the requirements vary a lot from species to species. The popular Amazon Sword (Echinodorus bleheri) will for instance grow quite big and need to be rooted in at least 8 cm of substrate.

Preventing disease

• Only buy plants that look healthy.
• Do not buy plats from aquariums where the fish seem unhealthy. Plants can carry malicious microorganisms and infect your fishes.
• If you want to be even safer, sterilize the plants before you place them in your aquarium. You can for instance use a dilute solution of potassium permanganate (provided that you have plant and fish species that can handle traces of potassium permanganate). Keeping a plant in potassium permanganate for 10-15 minutes will kill most malevolent microorganisms.
• Remove all damaged leaves before planting. It is better to remove a lot of leaves than allow them to decay and pollute the water.
• Do not panic if most leaves die, turn yellow or dissolve after planting. The shock of being repotted can make plants lose their leaves, but they will grow new ones.

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