Beginner’s Guide to 20 Gallon Planted Tank Lighting


Lighting is one of the most important aspects in your planted tank. It’s what makes you see, and it can make or break a beautiful aquarium. In this beginners guide to artificial lighting for tanks, we’ll go into some basics about how lights work, their advantages and disadvantages over time with different types of plants.

The “planted aquarium lighting calculator” is a calculator that will help you determine the light requirements for your new planted tank.

Tank lighting may seem unremarkable at first look. However, there is a snag:

When it comes to a 20 gallon planted tank, lighting is quite important. What’s more, guess what? If you make a one mistake, the whole arrangement will come crashing down.  

So, what should you know about lighting for a 20 gallon planted tank?

To begin, you must comprehend the significance of lighting. Then you must set a budget for purchasing the light based on the size of your tank, the intensity of the light, and the kind of light. Last but not least, you must understand how to set up and use the light you have purchased.

This is just a small portion of our comprehensive guide. Stay with us for another three minutes to obtain a comprehensive review of all you need to know about 20 gallon tank lighting.  

Let us now cast a light on the details-

Consider These Factors Before Purchasing Planted Tank Lighting

So, before you set up your 20 gallon planted aquarium lights, think about a few things, my buddy. 

As you can see, there are a few crucial questions that will help you decide how to set up your planted tank. So, what would such inquiries be? 

It’s OK if you’re at a loss for words at this point. That’s how we felt as well. As a result, we’ve condensed all of the deciding variables into five crucial questions. Now, let’s go through each of them one by one- 

Is CO2 Injection available to you?

The most critical ingredient in a planted tank is CO2. Your plant will no longer produce tons of CO2 on its own. CO2, such as API CO2 Booster, is required for a successful planted tank. 

What are the advantages of injecting CO2 now?

You can have strong illumination and attractive growth in the tank if you introduce CO2. Your plants will be able to live for a longer period of time. It’s not always necessary to put 20 liters of CO2 into a planted tank. If you have a 20 gallon low-tech planted tank, for example, a CO2 injection may not be necessary.

Because plants in a low-tech tank don’t always need CO2 to thrive. 

If that’s the case, you may skip the CO2 injection and instead focus on finding a nice light. 

Is the intensity of light the same for all plants?

Install Lights made of LEDs in Aquarium - Build My LED is a good place to start.

When it comes to lighting, the word ‘lumen’ is often used. Many of you may already be aware of this. 

But let’s go through this again to make sure we’re on the same page. So, what exactly is a lumen in terms of lighting? The entire measurement of visible light emitted by a certain source per unit of time is called a lumen. Your planted tank will look brighter if the lumen is greater.

In the area of indoor gardening, the light level/brightness is usually measured in lumens per square meter and lumens per liter of water.

You’ll also come across the phrase PAR, which is a highly essential term. So, what exactly does PAR stand for? 

The measurement of light output within the photosynthetic spectrum of 400-700nm is known as PAR, or photosynthetic active radiation. This photosynthetic range is used by plants to grow. 

Let’s attempt to learn a little bit more about lighting, shall we?

The strength of light varies from plant to plant, to be honest. Different sorts of plants may be found in the watery realm. However, there are three categories of plants if we split them based on their intensity. 

We’ve covered both the plants and the quantity of light they need for you down below-

PriceImageType of aquarium/planted tanka little quantity (watts per gallon)
Get Todaybeginner39s-guide-to-20-gallon-planted-tank-lighting-8859065beginner39s-guide-to-20-gallon-planted-tank-lighting-3453938a planted freshwater tank2-5
Get Today1650337446_115_beginner39s-guide-to-20-gallon-planted-tank-lighting-19531291650337447_60_beginner39s-guide-to-20-gallon-planted-tank-lighting-4908332Reef tank made of freshwater4-8

Is all of this information perplexing to you? 

Don’t be concerned, my buddy. We’ve got you covered! We’ve also calculated the light intensity based on the quantity of gallons for you. 

So, have a look at the table below.

Type of aquarium/planted tanka little quantity (watts per gallon)
a planted freshwater tank2-5
Reef tank made of freshwater4-8

You now know how much light the plant you selected need.

Also, bear in mind that if this amount fluctuates a bit, the plants will suffer. That is why, my friend, we recommend that you evaluate the light intensity in your 20 gallon tank using a light meter. 

You should look at various plant light meters that we’ve suggested.

PriceImageProductPros & Cons
Buy Now1650337449_830_beginner39s-guide-to-20-gallon-planted-tank-lighting-59282261650337450_177_beginner39s-guide-to-20-gallon-planted-tank-lighting-1329299Digital Illuminance/Light Meter Dr.Meter 1330B-VSwitches are convenient, but clearer instructions are needed.
Buy Now1650337451_242_beginner39s-guide-to-20-gallon-planted-tank-lighting-19477971650337453_491_beginner39s-guide-to-20-gallon-planted-tank-lighting-6347414The URCERI Light Meter is a device that measures the amount of light that enterWide variety of applications, although stronger Lights made of LEDs are required.

What Kind of Light Should You Purchase?

Yes, you read it correctly. When seeking for light, color or spectrum is highly essential. Why, exactly, do you inquire? 

So, you’ve seen the debate on PAR in the preceding section. The 400-700nm wavelength range we discussed has a variety of colors. These hues are also necessary for your plant’s photosynthetic function. 

As a result, you must educate yourself on the subject. is the source of this information.

This image, as you can see, depicts the relative photosynthetic rate of plants. So, what is the optimum color light for a fish tank?

Plants, on the other hand, need the hues green and yellow. These two aren’t a waste of time. For this reason, a broad spectrum light is ideal for a planted tank.

Now that we’re talking about lighting, it’s only natural to bring up the subject of temperature. 

Do you know what temperature a planted aquarium should be kept at?

It’s roughly 76-80 degrees Fahrenheit right now. Giving the proper hue and quantity of light is a basic rule of thumb for providing the right temperature.

There’s a lot more to learn about wavelengths and spectrums, to be honest. However, we don’t want to bore you with technical details. Because understanding the fundamentals we’ve supplied is all you need to get started cultivating plants. 

What Should the Light’s Length Be?

Let’s talk about the duration of the light now. A 72-inch LED planted aquarium light is obviously insufficient for a 20-gallon planted tank. Because that’s ludicrous. A person with a 125 gallon or larger tank, such as the 150 Gallon Starfire Glass Aquarium, may only utilize a 48′′-54′′ LED light. 

That’s why you should consider the size of your 20-gallon tank when planning your budget. 

We like making things as easy as possible for you. So, with that in mind, here are the tank measurements. A planted tank with a length of 20 gallons and a height of 20 gallons-

PriceImageFish TankDimensions(LxWxH)Added weight (LBS)
Get it right now.1650337455_900_beginner39s-guide-to-20-gallon-planted-tank-lighting-97580771650337457_322_beginner39s-guide-to-20-gallon-planted-tank-lighting-3652126Tetra Aquarium High 20 GallonApproximately 24″x12″x16″225
Get it right now.1650337458_713_beginner39s-guide-to-20-gallon-planted-tank-lighting-38361641650337459_31_beginner39s-guide-to-20-gallon-planted-tank-lighting-640256320 Gallon Long Aqueon AquariumApproximately 30″x12″x12″225

Now you know how big a light for a 20-gallon fish tank should be. If your tank is 20 gallons long, you’ll need a light that’s 24 inches long. Also, for the 20-gallon high one, a 30-inch long lamp.

Why a 30 inch led aquarium light, you might wonder? Your tank will receive the maximum amount of light or photons if you do so. No one in your tank will be deprived of light! 

It might be difficult to maintain the floating plants in one position at times. As a result, the light is obstructed, and the planted aquarium plants do not get enough light. This might be an issue. As a result, you should consider the duration of your light carefully.

What Kind of Lighting Do You Prefer?

close-up-of-fish-swimming-in-aquarium-at-home-742356665-5aa2bab2fa6bcc00377fd8b0-7689270 is a good place to start.

Isn’t it true that you’ve gathered a lot of knowledge on lighting by now? 

On that topic, the lighting requirements for a 10 gallon planted tank and a 20 gallon planted tank are not the same. Because for your 10 gallons, you may choose a regular or tiny bulb. Things become complicated when a 20 gallon is involved. 

There are several varieties of planted tank lights available now. However, we’ve included the most common ones for your 20-gallon tank below.

T5HO Light Source

T5HO is a thin high-output fluorescent tube that is 5 or 8inch in diameter. T5HO Light Sources are available in 24,39,54, and 80 watts. These lights come in blue and red colors as well. A T5HO fixture comes in 4,6, and 8 bulbs configurations. 

Should we use a t5ho aquarium light, then?

For your 20 gallon tank, we recommend the T5HO(ATI) fixture with four lights. Because it measures around 24 inches in length. As a result, it’s ideal for a 20-gallon tank. Now for the advantages and disadvantages of T5HO-

  • Produces a bright, steady light that has an excellent fluorescence. 
  • It’s fantastic for plant development.
  • Lights that are less expensive than others 
  • It’s not going to last long. As a result, it must be changed every one or two years.

We’ve recommended some of the best T5HO Light Sources for you-

Lights made of LEDs

Lights made of LEDs are very popular when it comes to planted tank lighting. More than 50% of the people who have planted tanks invest their time and money into Lights made of LEDs. LEDs also come in a wide range of watts and colors. 

You can use a 24-inch blue LED light for a 20-gallon long tank. Now, should you consider buying Lights made of LEDs? Let’s look at their pros and cons to help you make that decision-

  • It does not need a lot of energy.
  • It’s available in a variety of hues.
  • Long-lasting
  • Gives off a glistening appearance
  • Heat production is low.
  • The majority of models are pricey.
  • Only low-tech tank lights are cost-effective.

Some of our favorite and best Lights made of LEDs for 20 gallon planted tank are-

Now all you have to do is choose the ideal light for your lamp. Then start utilizing it to ensure that your plants and fish develop properly. 

How to Begin Using a 20 Gallon Planted Tank Light

A 20 gallon planted tank may be either 20 gallon long or 20 gallon high, as you may know. Fortunately, the instructions for both tanks are quite identical.

Prepare the Lighting

The first step after purchasing a planted tank light is to set it up. Now, be really cautious since we don’t want you to harm the vegetation or the fish. It’s not as difficult as putting up an air-cooled reflector, however.

Lights are sometimes accompanied with stands. So, if you purchase a light with a stand, you can simply position it next to your tank. is the source for this video.

If the light does not come with a stand, however, you may hang it on your own. There are two methods for setting up a 20 gallon planted tank–  

To begin, you may either build a shelf or hang the lamp from your ceiling. Second, you may mount the lights around your tank using a lighting rack.

For our planted tanks, we’ve experimented using these light hangers.

This isn’t all-

You should leave at least a few inches between the light and the tank’s rim while installing the light.

The gap for a T5 tube (ATI) should be around 10-12 inches, and for LED light such as solar RGB, the spacing should be 10-15 inches.

You can see a realistic demonstration of the whole setup and other nitty-gritty in the video below —


Keep your eyes peeled for the light.

You can’t leave the light on all the time. Why?

The solution is straightforward! Your aquatic plants don’t need as much light as you would think. You’ll get a lot of algae blooming in your tank if you supply too much light. As a consequence, you won’t be able to keep an eye on your 20 gallon planted aquarium’s plants or fish. This has a deleterious impact on plants and fish, causing them to die prematurely.

On the other side, if there isn’t enough light, you’ll suffer the repercussions. Your plants’ leaves will begin to yellow and finally fall off. Simply simply, your plants will perish and your fish will get unwell.

The question you’re probably asking now is: how much light is enough? 

You already know how much illumination you should offer. Because the quantities were indicated before in the section ‘Is the light intensity for all the plants different?’ As a result, be sure you’re barely inside the acceptable range!

After that, you must ensure that the illumination is timed correctly. You may do this by using a timer with your light.

Keep the illumination to a bare minimum while starting off with your planted tank. Your plants may prevent a stunning period by gradually lowering the intensity of the light from the start. 

So, how long should the aquarium lights be turned on?

For a high-tech planted tank with fast-growing plants, it’s OK to leave the lights on for 12 hours. Keep the lights on for 6-7 hours if you wish to make a low-tech cold-water tank.

Set your timer based on the results of this computation, and you’re ready to go!

The Advantages of Plant-Based Tank Lighting

In the long run, good lighting may save both you and your plant. There are two significant advantages of adding light to your 20 gallon planted aquarium:

Plant Growth That Is Simple

We all know that plants need a lot of light to develop. As a result, if you supply enough light to the plants in your aquarium, they will flourish. 

Your plants and fish will get unwell if you do not provide enough illumination. And you’re going to have a nightmare. That is why, for your 20 gallon tank, should add lights!

Color and attractiveness are improved.

Lighting, believe it or not, may make a significant impact in the appearance of your planted tank. So, if you’re wondering why a fish tank light is necessary– is the source of this information.

Whether you have a 20-gallon fish tank or a planted tank, the lights will instantly make it seem more attractive. You can see the interior clearly and quickly clean it if it becomes filthy. 

You can prevent your plants and fish having a hard time if the tank is clean and fresh. Instead, you may see them prospering and enjoying themselves in your tank. 

Three Crucial Points 

After all of the thorough information, it’s time for some useful hints. These will assist you in your efforts to light a 20-gallon high or 20-gallon long planted aquarium. As a result, let’s go right into the three most significant pointers:

  • For your 20 gallon planted tank, you can get away with using any type of light. Using a broad spectrum light, on the other hand, has a number of benefits, including preserving the colors of your plants.
  • It’s preferable to choose a lamp that matches the length of your 20-gallon tank. If you do so, you may simply prevent your plants from yellowing. 
  • It’s also crucial to keep the temperature under control. You’re doomed if the temperature in your tank rises beyond 80 degrees Fahrenheit. As a result, a thermometer may be used. A stick-on style thermometer is recommended.

After that, you may start thinking about 20 gallon planted tank ideas. You may either come up with your own ideas or get inspiration from the internet. In addition, for a beautiful touch, you may add fish to your 20 gallon planted tank. The possibilities and alternatives are endless!


What is the ideal light for a planted tank that is 20 gallons long?

You can go for Lights made of LEDs. You’ll find a lot of 24–30 inch Lights made of LEDs. You can find lots of good-quality Lights made of LEDs for your 20-gallon tank.

I’m not sure how long I’ll be able to keep the lights on.

Well, we’ve discussed this in detail (in the segment: Keep your eyes peeled for the light.). However, the ideal time is 8 hours. You can set your timer according to this time.

Is lighting an essential component of a 20 gallon planted tank setup? 

Without a doubt. You’ll need a decent light if you wish to cultivate plants. There are many nice lights available, so for your 20 gallons, pick a decent 24-30 inch light. 

What is the wattage need for a 20 gallon planted tank?

Wattage needs vary depending on the kind of tank. A good rule of thumb for freshwater planted aquariums is 2 to 5 watts per gallon.


We did our best to offer you with as much information as possible about 20 gallon planted tank lights. We wish you luck in reaching a resolution! 

So, what kind of light did you get for your aquarium?

Leave a comment to let us know. Plant aficionados, best of luck!

The “signs of too much light on aquarium plants” is a guide for beginners to help them identify when their tank has been over-lit. If you notice your plants are turning brown, it’s time to cut back the lighting.

Related Tags

  • cheap planted aquarium lighting
  • best light for 20 gallon high planted tank
  • aquarium lighting guide
  • best light for planted aquarium
  • rgb aquarium light

Leave a Comment