Lighting Requirements for Plants in Community Aquariums

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Much is said about special substrate, attention to fertilizers, and water conditions necessary to grow healthy aquatic plants. The fact is, with simple lighting and the right choice in easy-to-grow plants, every aquarium can have great live plants without much trouble at all. If your intention is to grow exotic rare species of plants, it’s quite another story, but with the common growth-oriented aquatic plants described in this article, no special expertise is required.

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    Good Lighting Requirements

    LED lighting is great for aquarium plants

    The Spruce / Thomas R. Reich

    Light is necessary for the photosynthesis required for the health and growth of all aquarium plants. Proper lighting enables the plants to absorb the carbon dioxide gases the fish breathe out. Too much light will cause the appearance of microscopic life known as algae. Too much light and a type of floating algae can grow that will turn the water green; too little light and plants suffer; but with the right level of light, some small spots of green algae appear on the surface of rocks and sides of a glass aquarium. Some algae are desirable, fish nibble on it, and it adds to the natural look of a healthy community aquarium.​

    In general, if an aquarium is near a sunny window, it may only need 5 hours of artificial light per day. But in direct sunlight, the algae growth will be out of control, even without any artificial light at all. For best results, an aquarium should be placed in an area where sunlight never reaches it directly. Artificial lighting should be on for a minimum of 8 hours per day but can stay on 10 to 12 hours if this enables better viewing in the evening for the hobbyist.

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    Replace Incandescent Lighting

    If you are using old-fashioned incandescent lighting, the lighting should be about 25 Watts per square foot of aquarium water. However, incandescent lighting is obsolete for several reasons:​

    • Incandescent lighting is inefficient at penetrating the water below 12 inches in most cases and does not evenly light the aquarium.
    • It causes excessive heat and can warm the water above the temperature you have the heater set to maintain, then allows the water to cool when the lighting is turned off.
    • Incandescent lighting is very expensive to operate compared to fluorescent and LED lighting.
    • Incandescent lighting bulbs have a very short lifespan, and can even break if splashed with water while turned on.
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    Fluorescent Lighting vs. LED

    Another type of available lighting for aquariums is fluorescent and compact fluorescent lighting. If a fluorescent lighting fixture is used, be sure to use the bulbs specifically rated for aquarium plant growth. The light spectrum needed for plant growth is entirely different than a fluorescent bulb one would find in the kitchen or office lighting. Do not use fluorescent light bulbs from a hardware store; they may fit within the fixture, but they are not ideal for growing aquarium plants.

    LED lighting has made amazing progress in the growth of exotic plants with some higher-end fixtures, but even the most inexpensive LED fixtures specifically made for aquariums will be adequate for successful and healthy plant growth in a community aquarium. LED lighting is best for 3 reasons:

    • Superior light penetration to as deep as 24 inches without special attention
    • The light spectrum of LED encourages plant growth even with the most common and inexpensive fixtures
    • The cost to operate most common LED lighting fixtures is less than 10% of the cost to operate the average incandescent lighting fixtures, and less than 30% of the cost to operate most fluorescent aquarium lighting fixtures.
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    Advantages of LED Lighting

    Aquarium Plants and LED Lights

    Aquarium Plants and LED Lights

    Thomas R. Reich, PhD

    Specialty lighting can be fun for effect within a community aquarium. 

    • One type of LED lighting for aquariums comes in a water-proof glass tube which allows it to be placed underwater, anchored by suction cups and behind plants. This can give a mysterious glowing effect to viewers, casting unusual rays of light coming out from behind plants and rock features.
    • Another specialty light available to aquarium hobbyists is a spotlight effect. Some are used above the surface to highlight one plant or piece of décor. Other types of “spot” effect lights can be anchored underwater shining up at a plant or feature creating interesting effects.
    • With the constant innovations coming from LED lighting, comes a remote-controlled version that allows an infinite variety of colors and intensities.
    • Commonly available within standard LED lighting fixtures made for aquariums is a “moonlight.” These lights are used in the “night time” cycle and allow the hobbyist to view fish behavior in the dark. The wavelength that creates the blue color can be seen by humans but does not interfere with fish sleep cycles or nocturnal activities of the catfish cleaning crew, shrimp, and other things that come out in the night.

    Continue to 5 of 7 below.

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    Timing Considerations

    It is advisable to use a timer to turn lights on at a set time and off at a set time every day. Consistency is necessary for best plant growth and for fish to develop a regular life cycle. Can you leave lights on 24 hours a day without killing your fish? Yes. Is it advisable or even humane? No! Setting the lighting to be on at least 8 hours to 12 hours per day is best, depending on the home schedule of the viewers. The community aquarium is there for your viewing enjoyment, so set the light cycle to be on when observers are more apt to be in the room. 

    Is it okay to turn on the lights if a visitor comes at an odd hour and wants to see the community aquarium in all its lighted glory? Yes, it is okay occasionally, but remember; it will take 20 to 30 minutes for the fish to fully “wake up” and become as active as they are in a normal light cycle. It is important to remember: a well-run community aquarium simulates nature as closely as possible. In nature, the sun comes up every day and goes down every day, and the sun does not come on in the middle of the night. Remember this when deciding to turn on the aquarium light out of the cycle. It is okay sometimes, but it is not natural to your fish and their life.

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    Why Plants Die

    Aquarium plant

    Aquarium plant

    The Spruce / Thomas R. Reich

    • If the roots get too hot compared to the water temperature. This could happen if the aquarium is over a floor heating register. It is never advisable to have an aquarium near or over a room’s heating source. When the roots are too hot compared to the plant itself, the plant can turn yellow and die.
    • A light source that is too weak in intensity for proper aquatic plant growth (old-fashioned screw-in bulbs for instance). Or the tank itself is too deep for the lighting fixture you have chosen; make sure to tell your dealer what size aquarium the lighting fixture is for. Different intensities are available for different depths of the aquarium.
    • The aquarium water pH is too acid.
    • Not enough fish to provide carbon dioxide and “fertilizer.”
    • True aquatic plants were allowed to dry out before planting in the aquarium.
    • Too many plants in the aquarium and the foliage at the bottom of the aquarium is being shaded from the growth-generating light by the plants above it.
    • Remember that plants with red or reddish color require special lighting and fertilizer to thrive. Avoid these as a beginner. Refer to the list of suggested plants for the community aquarium listed below.
    • The aquarium is not yet established, so there is not enough “fertilizer” from the fish built up yet. This can be remedied by adding commercially available aquarium plant food in liquid or tablet form.
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    Recomended Easy Plants

    This list makes no attempt to be complete or to go into the various species of each plant suggested. Some have roots, some have bulbs and others are bunch plants. What the plants on this list do have in common is they are all easy to grow and pleasing to the eye!

    • Anacharis
    • Sagittaria
    • Vallisneria
    • Ambulia
    • Ludwegia
    • Cyptocoryne willisii
    • Aponogeton undulatum
    • Amazon sword plant
    • Hygrophila
    • Myriophyllum
    • Cabomba
    • Cryptocoryne becketti
    • Hair grass
    • Nuphar lilies
    • Madagascar lace
    • Acorus
    • Nitella
    • Indian fern

Read More on Growing Aquarium Plants

Aquarium plants can become a major part of aquarium keeping for many hobbyists; there are societies for aquarium plant fanciers as well as books and websites that specialize in the joys of growing aquarium plants.

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