Do Planted Fish Tank Need Aquarium Lights

By Eddie Waithaka @aquariawise

Planted Aquarium Lights—Buying an Effective Fixture

Live plants are key to keeping a healthy aquarium environment. But all plants need light to grow, including aquatic species. The right light will help them take in the CO2 put out by fish and use that to spruce your tank.

However, choosing the perfect light for a planted aquarium can be time-consuming given the endless options in the market. Plus the inconsistent advice available online.

For this reason, I’ve prepared this article to help you know what to look for when buying your next aquarium plant light, whether online or from your local store.

But first, let me answer a common question across all aquaria forums!

Are Fluorescent Tubes Good for Aquarium Plants or Should You Switch to LED Light?

It’s very likely that most people will suggest you switch. I, however, don’t think it matters the type of lamp you use as much as the quality of light.

So if you ask me, I’d say you can still use fluorescents. But, pound for pound, LED lights are the harder hitter.

Fluorescent lamps have been the standard lighting in aquariums for years, mostly because they were effective with relatively low heat, plus they’ve stood the test of time and are easier on the pocket.

I have used an Aqueon full spectrum fluorescent to keep my plants beautiful for years and I’m still contented with the performance.

Realistically, LED technologies have improved exponentially and the lights source more economical, they’ve, however, only pushed fluorescents to number two.

Nevertheless, while the first generation LED grow lamps were simple with fewer color options to choose from, newer LED lights incorporate a larger array of colors. Which means they will replace fluorescent lights better than older LEDs if need be.

So, if you really have to switch, get a special LED set made for planted tanks, with the color spectrum that your plants need to grow and thrive.

Look for Photosynthetically Active Radiation (PAR) value of LED aquarium lighting options.

Choosing The Perfect Light for Your Aquarium Plants

Not just light, but proper light is important to successfully maintain a planted aquarium. Using the correct light will create healthy plants, keep algae at a minimum and give you the best viewing expirience.

Also, choosing the fixture that best fits your aquarium will keep you from buying the lights frequently.

That said, these are the aspects I consider every time I go out shopping for aquarium grow lights.

#1 — Light Intensity

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

The intensity varies depending on the lamp with both high and low-intensity bulbs available in the market.

In plant culture, young plants require cooler light intensity than vegetative and blooming plants. Whereas indoor plants require high-intensity light to compensate for the low natural light inside.

Green plants love bright light and dark green plant less light. Whereas plants with vibrant coloration that isn’t green thrive under bright light.

So, what is considered bright light or high light?

While gardeners refer to bright or heavy light as full direct sunlight, aquarists don’t. Because plants growing in tanks only need enough light to actively photosynthesis.

Therefore, for aquatic plants, heavy light is anywhere between 4 and 5 watts of fluorescent grow light.

Medium light is anywhere between 2 and 4 watts per gallon of fluorescent grow lights, and this is the range where most aquarium plants will grow.

Low light is just enough to see your fish and is usually included in startup tank kits. The light is less than 1.5 watts per gallon of fluorescent grow light.

Low light only grows the hardiest of aquatic plants that include: Java moss, Java fern, Anubias species, Amazon sword, Jungle Val, Water sprite, Rotala, Hornwort, and a few others. All of which will grow faster under medium light and some under heavy light.

However, while older lamps and bulbs are classified by how much electricity they use in watts, it’s difficult to compare that to newer LED fixtures which are classified in lumens.

Lumens refer to precisely how much light a particular light source gives off, while watts is how much power they consume. Both or either of the two values is written on the packaging of most lights today.

So to make it simple for you, if you plant hardy aquarium plants, use lamps with 10 to 20 lumens per liter. For medium plants, use lamps with 20 to 40 lumens per liter and more than 40 lumens per liter for advanced plants.

A pinch of salt if I may, while the following metrics are widely accepted, they are criticized in equal measures. The watt per gallon measure is considered by some too old and not quite helpful for LEDs.

Then if you are accustomed to the imperial system, the lumens per liter metric may just be pure greek to you.

#2 — Quality of Light: Spectrum

The light spectrum is a portion of the electromagnetic range which is a representation of multiple waves varying in frequencies.

The spectrum is measured using the Kelvin scale with light less than 5500K being more red and yellow, and as the Kelvins go up the light gets bluer.

In turn, chlorophyll A, B, and Betta Carotene in plants are pigments that capture most of the light used for photosynthesis.

Usually, the pigments are more efficient in capturing wavelengths that fall in the blue and red bands of light and are least efficient at capturing green and yellow light.

This optimal range is between 400 nm and 700 nm and is typically referred to as Photosynthetically active radiation range, often abbreviated PAR.

Therefore, using grow lights with the blue and red light wavelengths in your planted aquarium is more desirable.

Yellow, orange, violet, indigo, and green wavelengths are best when you need to bring out aspects of plants or fish to create a vibrant aquarium, but not for actual plants growth.

That said, it’s practically impossible to evaluate the quality of light by merely looking at a grow light.

For instance, a ray of light may look white to you but it is in reality made of many different wavelengths.

You could use a PAR meter but that will only tell you how much light to use, but not where in the spectrum the light falls and not the spectrum distribution either.

Meaning you can tell the quantity but not the quality. Plus, PAR meters can run you up about $350.

So, the best option is to purchase bulbs with specific terms like natural, full spectrum, or balanced and hope it’s not a marketing gimmick.

Usually, while normal incandescent bulbs only provide red light and cool white tubes blue light, full spectrum bulbs cover the whole spectrum from infrared to near ultraviolet.

To put this into perspective, sunlight is considered full spectrum even though the distribution reaching earth shifts with time, latitude and atmospheric conditions.

Therefore, the term full spectrum implies the bulb perfectly emulates the important qualities of natural light.

Unfortunately, products marketed as full-spectrum may produce light throughout the entire visible spectrum without producing an even spectral distribution. Hence some may not differ substantially from lights that are not full spectrum.

But some manufacturers now include the wavelength more precisely. Meaning it common to get an LED strip light described as “Cold white+blue+red color, ideal for freshwater fish and low- high-level plants”. Which, although you just have to take their word, is a little more descriptive.

#3 — Type of Light Bulbs

Aquarium light types are not all the same, sometimes it depends on the size of your tank. Other times it depends on the efficiency and economy of the lights.

For the longest time, the most common form of aquarium grow-lights were T8 and T5 fluorescent bulbs. Both of which are capable of growing plants.

However, T5 are recommended since they are more powerful and better suited for densely planted setups.

Today LED lighting has also made amazing progress in the growth of aquarium plants. Manufacturers have even made some pretty effective fixtures with multiple colors albeit more expensive.

Other forms are halogens, plasma, incandescent, and metal halide grow lights.


Of the three fluorescent lights, T5 are preferred because of their skinny bulbs, narrow footprint, availability, efficiency, and low heat output.

T5s also offer the best watt-to-lumen ratio which means they are both brighter, efficient and last about 10 times longer than incandescent bulbs.

The lights are particularly useful for young plants which unlike high powered metal halide bulbs are less likely to spike your tank’s temperature.

When using fluorescent lighting fixtures, replace the bulbs with specially rated types for aquarium plant growth. Do not just take any bulb from a hardware store, they could fit but won’t grow your plants.

You can also opt to either use T8 or T12 fluorescent lights. However, these are not as efficient plus T12 are large and it’s difficult to find blue bulbs for them.


LED lights bulbs are best for most aquariums, but those with enough output are expensive. However, even some inexpensive fixtures specifically made for aquarium use will be adequate for most plants.

LEDs have superior light penetration as deep as 24 Inches and the cost less to operate. Sometimes even less than10 percent the cost of operating the average incandescent lights, and less than 30 percent of the cost of operating most fluorescent lights.

Some LEDs lights even create fun effects in fish tanks. They come in waterproof glass tubes which are placed underwater or behind plants, which cast an unusual glow creating unique aquarium accents.

Also commonly available are standard moonlight LEDs which are useful in the night cycle. They don’t disturb the fish sleep pattern and at the same time allow the aquarium owner to observe fish behavior.

The blue light doesn’t interfere with either the sleep or nocturnal activities of the fish.

Other effect options available are the spotlight and remote-controlled versions that allow an infinite variety of colored intensities.


Incandescent bulbs are old fashion light systems, so if your fixture comes with this type of lighting, you’ll need a bulb change.

Apart from being an obsolete technology, incandescent lighting is inefficient at penetrating water below 12inches and bulbs do not adequately light the aquarium.

Plus these bulbs cause excessive heat which warms the water overriding any effort to regulate the aquarium temperature whether with a heater or chiller.

Another con is the operating cost of incandescent bulbs is prohibitive. Most bulbs will consume 90percent more power than your average LED light and only last for a really short time.

The best and reasonably priced alternative would be compact fluorescent light bulbs. You can even place desktop lamps with CFLs around and over the aquarium.

Combining the two is also feasible because incandescent bulbs only cover the red wavelength and average CFL bulbs the blue wavelength.

Metal Halide

Metal halides are very bright ranging from 100-400 watts and can create the desirable shimmering in your aquarium. However, these lights get quite hot while in use and mostly have to be placed over the aquarium.

They are only good for smaller deeper tanks but not exactly helpful to aquatic plants.

Also, metal halides are barely economical and since they get quite hot, will increase the tank temperature. Hence this heat can only be dissipated if you have a large tank with a lot of water.

#4 — Light Period

Since plants need a dark period to recharge for another day of growth, it gets to a point where you have to switch off your aquarium lights, though moonlight LEDs can come in handy in such instances.

Getting the light periods correct is important not only for your plants but to also prevent algae growth. If your light period is too long you will definitely get more algae.

Black lights are ideal to adequately illuminate your aquarium and display the aesthetics while still dark enough to allow your plants the much-needed rest.

The wavelength that creates the blue color is visible to the human eye but does not interfere with the plant or fish sleep patterns.

A substitute or complement to using black lights in the evenings is putting light timers. This will ensure your plants are getting the same amount of light each day.

In short, use normal LEDs or T5s during the eight to 14 hours of light when your plants are actively growing. Then set the timer to switch to black-light in the evening when the plant rest but you still need your aquarium to pop.

#4 — Light Fixtures

The only fixtures you would maybe be concerned about when shopping for aquarium grow lights is the hood, lid, cover or canopy.

In addition to housing your lights, aquarium hoods add visual interest to fish, keep the fish safe, direct the lights to your plants and reduce evaporation.

A thing to note is all hoods are not the same. Granted, you will have to pay attention to the specifications and dimensions of the model and brand.

When it comes choice, plastic hoods are considered to be the most common. There are two reasons why: first, they are budget-friendly and two, their roof like shape make them ideal for housing aquarium lights.

So, instead of having to deal with complicated custom lids, you can opt for plastic hoods that come with the light already attached. Which means all you have to do is just place them on your tank.

Aquarium hoods made of glass are an excellent choice if you want to combine elegant appearance and functionality. The clear lid will maintain water at optimal level ideal both for fish and plants and still look stunning.

Wooden aquarium hoods are used mostly for aesthetics purposed to complement stands or furniture in the aquarium room.

Enjoy your planted tank.

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