Aquarium Plants

Live plants are a wonderful way to beautify a freshwater tank and bring out the natural splendor of the fish that live in the aquarium.  Using different types of plants (colors and sizes) in different zones of the aquarium allows the creation of a wonderful 3-dimensional “green” backdrop.

Variety

The many varieties of plants available is almost overwhelming.  Despite this, they are relatively easy to classify and easy to learn care facts about them.  Essentially, plants fall into two categories: stem (or bunch) plants, and rooted plants. 

Bunch plants are those that grow in a mainly linear fashion.  In other words, there is a main stem that grows vertically and sends out leaves directly from this stem.  From each of the areas where leaves emerge (called nodes), roots can also grow, so that any section of this stem can become a full plant in a matter of time, given proper conditions.  In fact, this is how these plants are propagated, by cutting them about halfway up the stem, and replanting them in the substrate.  When planted they will grow vertically, again, and you can eventually harvest and replant the new plants to expand their collection.

Rooted plants are more like traditional plants in their orientation.  There is a root mass, from which emerge several stalks with leaves or leaves directly from the roots.  The leaves and stalks emerge in a rosette pattern (usually) and spread via more traditional means such as flowering, rootlets, and sending out baby plants on stalks.

Planting

There are special methods that need to be followed when planting aquarium plants.  Because their weight is supported by the water, many aquarium plants do not have rigid structures like those found in terrestrial plants.  Because of this, these plants are subject to damage if not handled correctly.  When planting bunch plants, the lead weight used to keep them submerged should be removed.  A loose rubber band can be applied to keep them together if deemed necessary.  Any tight constriction around the base of the plant, though can cause rotting and death.

In general, once the plant is ready to enter the tank, a spot should be chosen that is appropriate for the plant to grow with out disruption.  Next, cup the root ball or bottom of the plant and push the back of your hand onto the substrate, clearing out a divot.  Extending your fingers, place the plant’s roots into the divot and gently scoop additional substrate into the hole.  The gravel or substrate should not exceed the rooted area of the plant, similar to planting a terrestrial plant.

Lighting

Proper lighting is critical to growing aquarium plants. When looking at the spectrum of visible light, we see that the color shifts (from shorter to longer wavelengths) from purple to blue to green to yellow to orange and finally to red. Since plants reflect the green wavelengths (they look green to us), the spectra useful for most plants consists of red and blue wavelengths.

Without enough light, plants do not have the energy to grow or even live. Essentially, the more light on an aquarium, the better off it will be for the plants inside. Few plants have upper limits on lighting, because water can be an effective filter of light.  Regardless, there are groupings of plants that tolerate lower light levels, mid-level light, and those that require high intensity light levels.

Carbon Dioxide

Carbon dioxide, or CO2, is the source of carbon for building tissue in plants.  Naturally, having more of this around in a tank can enhance the growth of the plants. Generally, addition of CO2 to an aquarium is something done by hobbyists that are focused on plant keeping. There is high- tech and low-tech ways of going about this. The low-tech way consists of adding yeast, sugar and water to a clean 2-liter soda bottle and piping the resulting CO2 to the tank. The high-tech way comprises of a bottle of compressed carbon dioxide (in liquid form) and releasing it via injection to the tank. The high-tech way is more expensive initially but is much easier and cheaper to run in the long term. 

This method of adding carbon dioxide can be configured to run automatically, only needing maintenance to replace the canister when empty. A regulator is connected directly to the bottle.  This device controls the pressurized liquid inside, so that it flows out at a slow steady rate. If a solenoid valve is connected to the regulator, then there is a means to open or close the flow of CO2 with an electrical current. To fully automate this process, a pH monitor is used. This uses a pH probe placed inside the tank to measure the current pH level. The monitor itself can be set to trigger a current when the pH reaches a certain level. If carbon dioxide is added to a body of water, it combines with the water to form an acid, called carbonic acid. This is what changes the pH when carbon dioxide is added. When this monitor unit is attached to the solenoid valve, a fully automatic CO2 system is in place.

To further illustrate the point, say that we want to add CO2 to a tank, and the current pH is at 7.0.  If we attach the fully automatic injection kit to the tank, the probe (and therefore monitor) will see that the pH is at 7.0. However, we know that carbon dioxide is more soluble in water below pH 7.0, and plants will absorb it better at below pH 7.0. So, we aim for a pH of 6.5, and set the monitor to allow power to the solenoid until the pH reads below 6.5. When the solenoid is open, the pressurized carbon dioxide will escape into the tank, lowering the pH. At 6.4, the pH monitor shuts off power to the solenoid, preventing further CO2 from entering the tank. As plants use up the carbon dioxide, and it is liberated by filtration, the pH will rise again, and the monitor will turn back the solenoid back on again.

This process occurs automatically throughout the day and night. However, during the night, much less CO2 is taken up by the plants, so the pH will remain on the lower side, shutting off the system. If the injection system were not fully automatic, we would need to turn the system off at night or connect it to a timer that turned it off when the lights shut off.

Fertilizer

Just as with the more commonly known terrestrial plants, aquatic plants require certain nutrients for proper growth and health. In most aquariums, where both fish and plants are kept, there is a much-reduced need for additional plant nutrients because the waste products from the fish are readily absorbed by the plants. Again, by far, the more important components for keeping plants are light and carbon dioxide.

Beyond these keys, though, there are circumstances when extra nutrients should be added to the aquarium. Iron is an important nutrient for proper plant nutrition and can be supplied via a fertilizer. Other nutrients, such as manganese, boron, molybdenum, magnesium, nitrogen, phosphorous and potassium are also required in small or trace amounts. Most fertilizers supply all of these nutrients to the plants.

Fertilizers come in two forms: liquid and tablet form. The easier method of dosing is the liquid format, where a small amount can be measured out and then poured into the tank. This is not the ideal method, however, since most aquatic plants take up nutrients through the roots, and not the leaves, where the fertilizer is most abundant. Tablet fertilizers deliver the nutrients directly to the root balls and prevent much of the fertilizer from diffusing throughout the tank, feeding algae.