Lighting a Planted Aquarium

by Jul 14, 2022

How Do We go About Lighting a Planted Aquarium?

In a fish-only tank, you can see and observe your faunas. But in a planted aquarium, aside from aesthetics, the light you use is the energy source and the trigger for plants to create their own food (sugars). These sugars are used for plants’ metabolic processes. Light, along with water and CO2, are plants’ lifelines.

Without enough light in a planted aquarium, plants will take in oxygen and depletes the supply, and continually produce carbon dioxide. A complete deficit of oxygen will eventually affect all your faunas and good bacteria too – dead. Everything will turn into mush in 2-3 weeks. You essentially have an Ammonia tank by that time full of decomposing organic matter.

So how do we go about lighting a planted aquarium? What are the specifications that we need to know? What are the marketing gimmicks that we need to avoid?

Natural Lighting in Nature

Let’s say, what would happen if the sun disappeared suddenly in our solar system? We will not immediately notice it as light from the sun takes about 8.5 minutes to reach us. Nine minutes later, we will be in total darkness.

Without the sun’s magnetic field keeping us on our Goldilock’s orbit, we will be slingshotted and retain our forward motion. Every planet will fly off into outer space in a straight line.

Without light coming from the sun on earth: no plants, no phytoplanktons, no photosynthesis, and surely no oxygen as a byproduct of photosynthesis. Any animals, including us, that rely on plants for food, will be no more, and any predators, including us, who need these herbivores will be affected too.

Carbon dioxide as part of the greenhouse gases is not removed to some extent without plants. Oceans account for the most absorber of Carbon dioxide and the sun’s heat energy and distribute it evenly.

The Sun and the Earth

The Sun and the Earth. Image by Arek Socha from Pixabay

Forest Canopy

Forest Canopy

The earth is very good at keeping the heat but keeps on steadily cooling off. Within a year, the ocean’s top layers will freeze at global temperatures dipping below -100 F. The deeper layers will be continually insulated and remain liquid for the next hundreds of thousands of years.

But then the ocean’s deep layers will eventually freeze at a stable global temperature of -400 F. The atmosphere will collapse and will freeze too and come down on us (no protection anymore from all cosmic radiations). Ultimately, there will be no life on earth.

Imagine all these happening in total darkness as Earth continuously drifts into space aimlessly.

Plants and animals, including us humans’ Circadian rhythm is set by the light from our sun and affects our well-being too. It gives us the ability to see and discern colors.

Frozen Earth

A Frozen Earth by Kevin M. Gill. License and source link. No Changes.

How Much Light do You Need for a Planted Aquarium?

Our earth is much like a terrarium (for land ecosystems) or a planted/marine aquarium (for freshwater or marine ecosystems) on a planetary scale with the sun as its light and heat source. It is beautiful and awe-inspiring when everything is in balance.

The thing is, as I always mentioned before, every planted aquarium is unique. There are no secret LED or T5 lighting specs, nothing set in stone. Even DIYs can work. There are many variables to consider when determining the proper lighting for your planted tank.

What light source to use (can we use sunlight)? How big is your tank? What is the right spectrum? DIY or not? What plants are you keeping? What is the design of your aquascape? What lighting intensity and how to adjust?

Do I have to bombard my plants with 100 % of my light by default? How long should I turn it on? Should I use a timer and dimmer? Narrow or wide light spread? Your budget comes into consideration too.

Sunlight, Forest, and Stream

It is easy to get lost in the decision making but don’t be disheartened though. For a beginner or even an intermediate aquascaper, some of these terms, tables, and charts might be a little overwhelming to grasp.

But arming you with the right lighting knowledge, you can adjust and decide your lighting requirement based on your planted aquarium needs. So here are the basics and the most critical factors to consider in lighting a planted aquarium.

Dutch with some Elements of Nature Style Aquascaped by Lester Plata Philippines using Chihiros Vivid v2 Lights

Dutch with some Elements of Nature Style Aquascaped by Lester Plata Philippines using x2 Chihiros Vivid v2 Lights

Iwagumi Style Aquascaped by Matthew Manes Philippines - client used ATLEDTiS Cookie+ LED Light

Iwagumi Style Aquascaped by Matthew Manes Philippines – client used ATLEDTiS Cookie+ LED Light

How Big is Your Tank?

Tall tanks require you to use stronger lighting. Light waves decrease exponentially as it travels deeper into the water. Long tanks that have more width than height are a good starting point. 

10, 15, or 20 gallons ‘long’ are good choices to start with. Avoiding tall tanks saves you from overexerting yourself while doing the designing of your scape or while doing maintenance/trimming.

You can still use standard tank sizes but be prepared for the additional cost in electricity bill and the stronger lighting requirements. I did some adjustments to avoid these.

For example, I have a standard 35 gallons tank on our terrace. I have lots of ambient light but no direct sunlight. I used a Chihiros A plus White LEDs 60 to 80 cm before.

My light is about 22 inches from the substrate and only at 80 % intensity. I choose to keep mostly undemanding plants and carpets.

When I upgraded to LEDStar D60, which has WRGB LEDs and the same height, I adjusted the intensity to 70%. I am keeping mostly Epiphyte plants and Micranthemum Monte Carlo as carpet.

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I also used Dwarf Hair Grass, Microswords, and Hydrocotyle Tripartita with great results. Nowadays, I am just using Cryptocoryne Parvas. They don’t require trimming for many months.

Couple that with injecting only two bps CO2, I can still grow full-blown carpets, have some coloration on plants, dose leaner on fertilizers, minimal to no visible algae, and weeks between trimmings.

Eventually, I will use my old Chihiros at 50% intensity in my Riparium, mostly keeping marginal terrestrial plants, emerged epiphyte plants, and submerged Cryptocoryne. I DIYed a hanging fixture for my Chihiros LED Light 17 inches from the top of the storage box and about 32 inches from the submerged Cryptocoryne sp.

Nature Style Aquascaped by Allen Myung-hee Philippines using DIY UFO Light Lamp

Nature Style Aquascaped by Allen Myung-hee Philippines using DIY UFO Light Lamp

Hardscape Diorama Style Aquascaped by Poci Jacildo Philippines using x3 Dymax SpaceX LED Light

Hardscape Diorama Style Aquascaped by Poci Jacildo Philippines using x3 Dymax SpaceX LED Light

Most planted aquarium LED lightings have L brackets to fix them on the top of your aquarium. On some models, you can also hang them. That way, you can also adjust the height of your lighting. We don’t have to bombard our plants with 100 % intensity in most cases and wonder, why do I have an algae infestation? Yes, you should be able to adjust it.

It could be that your lighting is too strong but don’t forget that you may have other imbalances going on. (water parameters, over or under-dosing fertilizers, filtration not enough, overfeeding or overstocking, inconsistent CO2 injection, etc.)

The length of your lighting should span at least 80 % of your tank’s length to have uniform coverage. If there is no model of your chosen brand that can span your tank’s length, you have to install 2-3 of that model, or look for another brand.

Dutch Style Aquascaped by Lyn Jonie Philippines using Chihiros WRGB LED Light

Dutch Style Aquascaped by Lyn Jonie Philippines using Chihiros WRGB LED Light

Iwagumi Style Aquascaped by Alfred Repani Estrella Philippines using x2 120 cm Hepo LED Lights

Iwagumi Style Aquascaped by Alfred Repani Estrella Philippines using x2 120 cm Hepo LED Lights

What is the Right Light Source?

Nowadays, we only have two feasible choices: LED and T5 fluorescent lights. But we still don’t see any more reasons to use fluorescents as LED lighting for planted aquariums have come a long way and can achieve the same results, even better, compared to fluorescent lights.

LED lighting can do this while generating less heat, is very energy efficient, has a long life span (average 4-6 years, much longer if not 100% intensity and not subjected to excessive heat), has good spread, and will not cause a dent in your electrical bill.

There is no more proof of their popularity as most of the examples here are using LEDs. Some brands/models have automatic on-off/timers and dimmers to simulate dusk and dawn. They are convenient to fix and install on our tanks by L brackets that come with it or by hanging.

You can even customize the intensity of each individual LED color on some WRGB models by installing an app on your smartphone. They even have built-in heat sinks and fans to further bring down the operating temperature of the LEDs for more lifespan.

If you know electronics and building skills, you can DIY/experiment with your light fixture with LED bulbs or high-powered LED beads. Some had success with LED floodlights, even 5730, 5630, 5050, and 3528 LED strips.

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Fluorescent lighting (T5s), while cheap, will still put a dent in your electricity bill (much more with HOs – high output). It is still the most common light source globally and is easily available. Only 40-60% of the energy is converted to light. So less efficient than LEDs.

T5 Fluorescents also come in different colors like warm/cool White, Red, Green, Blue, Pink, Purple, etc. and you can customize/combine colors in a single fixture. The fixtures are bulky, including the ballast circuit, though, and more inconvenient to install.

The only ways you can adjust the intensity of T5s in a fixture are by subtracting/adding tubes or adjusting the height higher or lower.

So our recommendation is? Choose LED lighting for your planted aquariums. There are just no better alternatives for LED.

Dutch Style Aquascaped by Gilbert B. Dela Cruz Philippines using Week Aqua L600 Series LED Light

Dutch Style Aquascaped by Gilbert B. Dela Cruz Philippines using Week Aqua L600 Series LED Light

Dutch Style Aquascaped by John Michael Caamic Rivera Philippines using Chihiros WRGB90 Series v1 LED Light

Dutch Style Aquascaped by John Michael Caamic Rivera Philippines using Chihiros WRGB90 Series v1 LED Light

Dutch Style Aquascaped by Julaton B. Poy Philippines using Week Aqua L600 LED Light

Dutch Style Aquascaped by Julaton B. Poy Philippines using Week Aqua L600 LED Light

Not all LEDs are equal, though. They vary in quality, colors (spectrum), voltage or current controlled, wattage, lifespan, output, etc. Just be wary of those LED lights included on starter tank kits, as they are usually not enough to grow plants.

Planted aquariums LED lighting brands already did their R&Ds and testings (sometimes, with a few marketing gimmicks), and they have selections at any price point (they all can grow plants). But if you really want to realize the true potential of your plants (in terms of colorations), we really need to invest in our lighting.

Remember, lighting is just one variable in a planted aquarium equation. You still need to find the balance of everything and couple that with good planted tank fundamentals and husbandry. Our timely adjustments are still the key!

We will not even mention Incandescents or Metal Halides (Ooops!) unless you want to grow chickens.

Iwagumi Style Aquascaped by Ayong Go Philippines using Chihiros Vivid v1 LED Light

Iwagumi Style Aquascaped by Ayong Go Philippines using Chihiros Vivid v1 LED Light

Nature Style Aquascaped by Ramz Usman Mohammad Philippines using Kandila x2 90 cm LED Light

Nature Style Aquascaped by Ramz Usman Mohammad Philippines using Kandila x2 90 cm LED Light

How Much Light Intensity?

You may ask this yourselves at some point: “am I providing enough light in my planted aquarium?”, “how do I measure it?”, “do I just observe my plants and pray?”

There are really no exact numbers to answer those questions. As I mentioned above, every planted aquarium is unique. We all have different sizes of tanks, light sources, styles, water parameters, plant mass, stocking, filtration, etc.

Plants can adapt to whatever light we have given them. It is possible to grow healthy and lush plants at any given price point, even with DIY LED lighting and T5s.

Hardscape Diorama Style Aquascaped by James Ducut Philippines using Ista RGB LED Light

Hardscape Diorama Style Aquascaped by James Ducut Philippines using Ista RGB LED Light

Again, just be wary of those LED lights included on starter tank kits, as they are usually not enough to grow plants.

Extra colors like red, orange, purple, violet, etc. in our plants are just a bonus but are the goal for anyone who loves Dutch-style aquariums, as you can see from the many examples here.

But enough of that ramblings, so do we have some sort of general rules of thumb to gauge how much light intensity we are giving our plants?

To be honest, I didn’t even know these parameters when I was starting. I can still grow plants, but with some problems (not caused by the DIY light alone), and I will explain later.

Hardscape Diorama Style Aquascaped by Chuck Llorca Cajilig Philippines using NuniQ LED Light

Hardscape Diorama Style Aquascaped by Chuck Llorca Cajilig Philippines using NuniQ LED Light

Lumens per Liter or Gallon

Lumen is the measure of the quantity of visible light emitted by a source but takes into account the human’s eye sensitivities to various colors.

Do you see the obvious problem here? Plants don’t have eyes, and we humans are not plants!

Human eyes are more sensitive to green, so it will have more lumen value. However, plants use more red and blue when they are photosynthesizing. Red and blue have less lumen value but plants like them more. So scratch this.

Hardscape Diorama Style Aquascaped by Edrian Corpuz Espiritu Philippines using RGB Chihiros and LedStar Z Series LED Lights

Hardscape Diorama Style Aquascaped by Edrian Corpuz Espiritu Philippines using RGB Chihiros and LedStar Z Series LED Lights

Watts per Liter or Gallon

The oldest measurement to gauge the amount of light appropriate for the plants in our planted aquariums. But watts per liter or gallons are without controversy. Watts is the measure of electrical power, not the light output. In terms of lighting, it is used to quantify the rate of energy transfer, from electrical energy to light/heat energy.

So on this side, we have old aquarists that agree that it can give us a rough guide of the amount of light our planted tank needs. That is from their years of experience and familiarity with T5s or T8s. Giving that advice to a new hobbyist who has zero knowledge about the topic will be more of a hindrance than a help.

And on the other side, we have aquarists disputing that it was a technique developed decades ago when semiconductors (thus LEDs) were not yet invented. We only had fluorescents, metal halides, and incandescents before, and it makes no sense anymore with the advent of LED lighting. Why?

Because LEDs give off the same level of light as T5 fluorescents but with much less wattage. You will likely have an algae-fest or kill your plants if you try to match old T5 or T8, including their ballast watts, with the energy-efficient LEDs available today.

Hardscape Diorama and Nature Style tanks Aquascaped by Louise Sy Philippines using Chihiros RGB90 LED Light

Hardscape Diorama and Nature Style tanks Aquascaped by Louise Sy Philippines using Chihiros RGB90 LED Light

Iwagumi Style Aquascaped by Matthews Saliot Philippines using LEDStar AQ C Series 40 cm

Iwagumi Style Aquascaped by Matthews Saliot Philippines using LEDStar AQ C Series 40 cm

Nature Style Aquascaped by Ned Principe Philippines using Week Aqua L600D Pro LED Light

Nature Style Aquascaped by Ned Principe Philippines using Week Aqua L600D Pro LED Light

Here Comes PAR to Save the Day! What is PAR?

PAR stands for Photosynthetic Active Radiation. It measures the amount of light available for our plants to create their own food, to photosynthesize in µmols unit. But it isn’t without controversy.

PAR meters are expensive for most hobbyists. It can run you up to about 375$. Yes, almost as expensive as most high-end LED planted aquarium lighting models/brands. Some manufacturers provide PAR readings but only on their high-end models.

Take note of their PAR readings if they are measured near the light source or at a certain height underwater (ex. 30 cm is about 12 inches – substrate level on long tanks). Obviously, PAR readings are the strongest right below the centerline of the light fixture, decreasing as more distance from the centerline as it approaches the substrate. They usually take their readings on a filled tank.

For the models/brands that you are eyeing that don’t have PAR readings from manufacturers, a simple google search will help you find other hobbyists’ measurements on forums that have PAR meters. Sometimes, as generous as measuring PAR on different depths.

Nature Style Aquascaped by Apz Kevin Philippines using Kandila S Series LED Light

Nature Style Aquascaped by Apz Kevin Philippines using Kandila S Series LED Light

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