Simple Signs of Too Much Light on Aquarium Plants

aquarium light

The lighting requirements for an aquarium with live plants are more specific.

Plants need light for photosynthesis, a process by which plants use the energy from sunlight to produce food and oxygen from carbon dioxide and water.

Note: Plants will not survive in the aquarium unless there is adequate lighting for photosynthesis.

Since this light energy comes from natural sunlight, it is necessary to provide full-spectrum lighting in an aquarium to simulate this environment.

Signs of too much light on aquarium plants

signs of light

If your plant gets too much light, its leaves will have burnt tips, burn spots, or fall off

  • When only the most aggressive plants grow well, and the less aggressive ones stop growing.
  • Increase in the number of brown algae in the aquarium.

How many hours of light do aquarium plants need?

Most aquariums require 8 to 12 hours of light every day (10 hours on average), provided by the aquarium lighting system.

How much light is needed in your aquarium?

This is a large area, however, and determining how long to turn on the aquarium lights each day depends on factors such as

1. The level of Algae in your aquarium

Too much light leads to more algae growth. Reduce the on-time of the aquarium lighting to eight hours or a little less if needed, to reduce algae growth.

Monitoring algae levels can then help you determine if your lighting levels are appropriate.

If you start seeing too many algae, shorten the light periods to retard algae growth. But remember, you don’t want too little light for aquarium plants.

Direct sunlight tends to produce more algae than artificial light.

An aquarium near a sunny window may require less additional lighting than one on an interior wall.

2. The number of ambient lighting present in the room where the aquarium is positioned.

Determining the operating time of the aquarium lighting depends on the amount of ambient light already available in the room.

It’s also possible that you don’t need any additional lighting if your aquarium is in a bright south-facing conservatory with many windows, for example, or in an active family room with ceiling lights and lamps on most of the time.

However, room lighting is often more indirect, and chances are you’ll need to turn on the aquarium lights every day, regardless of how much light is already in the room.

However, a room with good ambient lighting does not require 12 hours of aquarium lighting.

3. The type and number of live plants present in the aquarium.

If there are live plants in the aquarium, you will probably need to maximize the additional lighting time.

Plants require up to 12 hours of light per day, but the exact duration depends on the aquarium setup and the type of plant.

Conversely, if your aquarium does not have live aquatic plants, your lighting needs are lower, just what the fish needs.

It is usually recommended to match the aquatic plants in your aquarium to the type of fish you keep:
Tropical plants for tropical fish aquariums;
Temperate cold water plants for aquariums with cold water species.

Lighting conditions should also be chosen to match the plants’ natural environment.

4. The species of the fish in the aquarium

Some species, such as Cichlids and Tetras, thrive with less light and, for these, excessive aquarium lighting can negatively affect them.

Consider the conditions a species will face in the wild to determine how much additional lighting if any, might be needed.

Tropical fish have evolved under conditions that provide around 12 hours of light each day.

So logic suggests that an aquarium with tropical fish will likely need a combination of ambient lighting and an aquarium for about half a day.

Signs of light deficiency on aquarium plants


signs of light deficiency

When your plant isn’t getting enough light, the most common signs are yellowing and dropping leaves, stunted growth, elongated stems, and dull green colour.

Signs of adequate light supply on aquarium plants

When your plant receives the right amount of light, it will have a deep, pleasant green colour.

And overall, you need to know the entire history of the plant and its growth pattern.

Many of these symptoms can have multiple causes, so context is essential.

Blue light for aquarium plants, Good or Bad?

Blue LED lights, which are mostly sold as moonlight bulbs, work well for aquarium fish.

They create a calm blue hue that allows your shy fish to venture out and feed at night, while fish that are only active during the day rest.

Moonlight bulbs also give you a beautiful display of your aquarium without worrying about the hassles of using a flashlight.

However, blue light works magically best on plant pigmentation, which means that most of your red plants will become “redder” when exposed to intense red and blue light, especially when paired with nutrient dosing.

Red lights for aquarium plants

Red lights are beneficial as they allow you to observe shy nocturnal fish at night without stressing them.

There is a common belief among fish keepers that fish cannot see red light.

And while there is no fact in the discussion, water absorbs red light more readily than blue light, which means that the use of red light encourages bottom fish to go out and play.

And to reiterate, red light is also used by aquarium plants, significantly to stimulate flower growth and development in fewer than a handful of plants that bloom in an aquarium.

Light also promotes pigmentation in red plants.

Unfortunately, you can only use red lights in moderation as algae use the red frequency for photosynthesis and only a small portion of that spectrum slows algae growth.

Can I leave my aquarium light on 24/7?

No, the tank lighting should not be left on for more than 12 hours per day.

All fish require periods of darkness, similar to those found in their natural waters.

By leaving the tank light on 24/7, the algae will overgrow and potentially harm the fish.

Choosing the best light for your aquarium plants


aquarium bulb

Using the right light will produce healthy plants, keep algae to a minimum and give you the best visibility.
Here are a few things you need to consider when choosing a light for your aquarium plants.

1. Light Spectrum (Quality of Light)

The spectrum of light is a part of the electromagnetic range that represents different waves, the frequencies of which vary.

The spectrum is measured using the Kelvin scale, with light below 5500K being more red and yellow, and as the Kelvin increases the light becomes bluer.

Chlorophyll A, B and betta carotene in plants are, in turn, pigments that capture most of the light used for photosynthesis.

Pigments usually capture the wavelengths that fall in the blue and red light bands most efficiently and least of all green and yellow light.

This optimal range is between 400 nm and 700 nm and is generally referred to as the photosynthetically active radiation range, which is often abbreviated as PAR.

Hence, using blue and red light wavelengths to grow lights is more desirable in your planted aquarium.

The yellow, orange, purple, indigo, and green wavelengths are best when you need to highlight aspects of plants or fish to create a living aquarium, but not for actual plant growth.

2. Type of Light Bulbs

The types of aquarium light are not all the same; sometimes, it depends on the size of your aquarium.

In other cases, it depends on the efficiency and economy of the appliances.

The most common form of aquarium grow lights for the longest time has been the T8 and T5 fluorescent lights.
Both are capable of growing plants.

However, the T5 is recommended as it is more powerful and more suitable for densely planted installations.

a. Florescent
Of the three fluorescent lamps, the T5s are preferred for their light bulbs, small footprint, availability, efficiency and low heat output.

T5 also offers the best watt-to-lumen ratio, which means they’re both brighter, more efficient, and last around ten times longer than incandescent bulbs.

b. LEDs
LED bulbs work best for most aquariums, but those with sufficient power are expensive.

Even a few inexpensive devices made specifically for use in aquariums will suffice for most plants.

LEDs have a higher light transmission of up to 24 inches, and the cost of ownership is lower.

Sometimes less than 10% of the operating cost of the average incandescent lamp and less than 30% of the operating price of most fluorescent lights.

c. Incandescent
Incandescent lamps are outdated lighting systems. So if your light is equipped with this type of lighting, you will need to change the bulb.

In addition to being an outdated technology, incandescent bulbs cannot effectively penetrate water below 12 inches, and incandescent bulbs do not adequately illuminate the aquarium.

d. Metal Halide
Metal halides are very bright and range from 100 to 400 watts. You can create the desired sparkle in your aquarium.

However, these lights get quite hot during use and most of the time need to be placed on the aquarium.

They are only suitable for smaller, deeper tanks, but aren’t exactly useful for aquatic plants.

3. Light Intensity

Light intensity refers to the strength or amount of light produced by a particular lamp source.

Intensity varies by the lamp, with both high and low-intensity lights available on the market.

In plant cultivation, young plants need a cooler light intensity than vegetative and flowering plants. At the same time, indoor plants need high-intensity light to compensate for the low levels of natural light indoors.

Green plants like bright light and dark green plants prefer less light. In comparison, plants with a vivid tint that is not green will thrive in bright sunlight.


Most of the time, signs of too much light on aquarium plants are always evident because there will be changes in the morphology of the plants and their surrounding environment.

So if you notice, any of the signs listed above on your aquarium plant, you should take proper measure to save your plants from dying off.

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