How To Measure PAR In The Aquarium

Aquarium lovers understand that making a great home for their underwater buddies is like being an artist. There are many things that help fish and corals stay healthy, and one important thing is called ‘photosynthetically active radiation’ or ‘PAR’ for short. 

In this detailed guide, I’ll take you into the world of PAR. We’ll learn what it means, why it’s super important for reef tanks, and how to measure PAR in the aquarium, and I’ll even share some top PAR meter recommendations. So let’s get started.

What Is PAR?

PAR, or Photosynthetically Active Radiation, is like the special kind of light that plants and corals really need. 

It’s the light that helps them make food through a process called photosynthesis. This unique light comes in a range of colours, from purple to red, and it’s found between 400 and 700 nanometers (nm). 

Imagine it as the energy source that keeps the plants and corals in your aquarium happy and healthy. So, if you want your underwater garden to thrive, you must ensure they get the right amount of this unique light.

What Is The Importance Of PAR In Reef Tanks?

1. PAR As Essential Fuel: PAR is like the essential fuel that powers the growth and daily activities of the corals and other creatures in your reef tank, similar to how food gives you energy. It’s a special kind of light that helps these underwater beings stay alive and grow.

2. Colour and Growth: The kind of light (PAR) and how bright it is can change the colours and how big corals get. Different corals need different amounts and types of this special light to stay colourful and grow well. 

If they don’t get the right light, they might lose their vibrant colours and have trouble growing big and strong.

3. Special Relationships: Corals have a special partnership with tiny algae called zooxanthellae. These little algae live inside the corals and use PAR to make food. 

In return, they give the corals the nutrients they need. But if there’s not enough PAR, this partnership can break down, causing the corals to lose their colour and become weak or even die.

4. Overall Tank Health: Making sure there’s the right amount of PAR is super important for keeping your whole reef tank healthy. 

If the corals and other light-loving creatures aren’t doing well, it can affect all the other animals in the tank that depend on them for food and shelter.

5. Measuring And Adjusting: You can use special tools to measure the amount of PAR in your tank. If it’s not quite right, you can change things like the type of lights you use or where you put them to make sure your corals and other creatures get the perfect amount of PAR.

6. Different Depths: Remember, the deeper the water, the less PAR there is. So, you need to choose corals and other creatures that are okay with the amount of light they’ll get in your tank, depending on where they are.

In short, PAR is like the lifeblood of your reef tank’s light-loving creatures. It’s the power that keeps them going and makes your tank a vibrant and healthy place for underwater life.

What Is The Recommended Amount Of PAR For Coral?

Different types of corals need different amounts of PAR, which is like the special light they need to stay healthy. 

  • SPS Corals: These are like the sun-loving corals. They need a lot of PAR, around 250-450 units of this special light. It’s like giving them a sunny beach to thrive.
  • LPS and Soft Corals: These corals are a bit more chill. They do well with less PAR, about 50-250 units. 

Getting the right amount of PAR is crucial. If you give too much or too little, your corals might not be happy. 

They could lose their vibrant colours or struggle to grow. So, it’s important to find out the PAR needs of your specific corals to make sure they’re getting the perfect amount of light.

You can do some research or ask a marine expert about the PAR levels your coral buddies prefer, and then adjust your tank’s lighting to match their needs. 

What Is The Importance Of It For A Successful Reef?

Here’s why PAR is so important:

1. Food Factory: PAR is like the reef’s main source of energy. It’s similar to how our bodies need food to stay strong and healthy. 

Corals and some other creatures in the reef tank use PAR as their energy source instead of food. This energy is super important because it keeps them alive, growing, and in good health.

2. Colorful Beauty: When the reef gets the right amount of PAR, it’s like turning on colourful lights underwater. Corals, in particular, show off their bright and beautiful colours. It’s like a natural light show in your tank, making it visually stunning.

3. Health And Growth: Just as we need the right nutrients to grow, corals and other creatures in the reef need the right amount of PAR for healthy growth. Without enough PAR, they might not grow properly, and their health could suffer.

4. Balance And Ecosystem: In the reef tank, everything is connected, like a big puzzle. When corals and other creatures get the energy they need from PAR, it helps maintain the balance of the whole ecosystem. It’s like each piece of the puzzle fitting together perfectly to keep the reef healthy and thriving.

In summary, PAR is like the life-support system for your reef tank. It’s the essential light energy that your corals and other photosynthetic creatures need to thrive, show off their colours, stay healthy, and keep your underwater ecosystem in harmony. 

So, making sure you have the right amount of PAR is a key factor in the success of your reef tank.

Instructions On How To Read PAR Tables

PAR measurement
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PAR tables are like special maps for your aquarium’s lighting. They show how bright the light is at different spots and depths in your tank.

These tables help you know if your corals and other creatures are getting enough light. It’s important because some need more light than others to thrive.

  • Select The Depth: Decide how deep in your tank you want to check the light. It’s similar to choosing a level in a swimming pool.
  • Choose The Location: Determine whether you want to know about the light at the bottom, middle, or top of your tank. Think of dividing your tank into different sections.
  • Read The Numbers: Look at the numbers in the table for your chosen depth and location. These numbers tell you how strong the light is in that part of the tank. Higher numbers mean a brighter light.
  • Compare With Needs: Compare these numbers with what your corals and aquatic friends require. Some creatures prefer lots of light, while others like it dimmer. It’s like making sure your plants get the right amount of sunshine.
  • Adjust As Necessary: If you discover that the light isn’t ideal for your corals and creatures, you can make changes to your tank’s lighting to ensure it’s just right for them.

What Happens If There Is No PAR Data?

Sometimes, you might not have the information about how much light your aquarium gets, and that’s okay. It can happen if you don’t know the exact details about your lighting system or how it works with your tank.

In such situations, it’s a good idea to reach out to experienced people who are skilled at taking care of aquariums. These experts are called “aquarists.” They have knowledge about different types of aquarium setups and can offer you guidance.

Another helpful option is to contact the company that made your aquarium lighting equipment. They can provide valuable information about how your specific lighting system works and how to use it effectively.

The important thing to remember is not to guess or make assumptions about your tank’s light levels. Accuracy is really important when it comes to creating the right environment for your reef and its inhabitants.

Selecting A PAR Meter

Picking the correct PAR meter is really important to make sure you get accurate measurements of the light in your reef tank. Accuracy is key to keeping your corals and other underwater creatures healthy.

  • Measurement Range: You want a PAR meter that can measure the full range of light levels in your tank. It’s like having a ruler that can measure everything from the tiniest to the biggest things.
  • Accuracy: Your PAR meter should give you numbers that are very close to the real light levels in your tank. Accuracy means you can trust the numbers it shows you.
  • Ease of Use: It’s important that the PAR meter is easy to use and understand. You don’t want something complicated that’s hard to figure out. It should be like using a simple tool.
  • Budget: Think about how much you’re willing to spend. PAR meters come in different price ranges. Consider what works best for your budget while still meeting your needs.

Here are a few PAR meters that many people have found to be reliable for reef tanks

  • Apogee MQ-510: This is known for its accuracy and ability to measure a wide range of light levels.
  • Seneye Reef Monitor: It’s user-friendly and provides valuable data for reef enthusiasts.
  • Milwaukee Instruments MC510: Budget-friendly choice with reliable performance, suitable for beginners and seasoned hobbyists alike.

Getting the right PAR meter helps ensure your reef gets the light it needs for success.

Instructions on How To Measure Par In The Aquarium

Step 1: Prepare Your Aquarium

Before you start measuring light for your corals, it’s essential to get your aquarium in the right condition

Inspect the lighting system in your aquarium. Ensure that all the lights are in good working order, including any specialized lighting you may have for your corals.

Look for any burnt-out bulbs or damaged fixtures. Replace or repair them as needed to ensure even and consistent lighting.

Make sure that your aquarium lights are following their usual schedule. Corals, like many living organisms, rely on a regular day-night cycle.

Check that the lights are turned on and off at the same times as they typically are. Consistency is key for the health of your corals. While preparing your aquarium, also keep an eye on the brightness of the lights. Ensure they are set to the usual intensity.

Some corals have specific light intensity requirements, so it’s crucial to maintain the right level for your particular corals.

Step 2: Get Your PAR Meter Ready

If you have a PAR meter, which is a tool to measure light for your corals, you need to prepare it properly before taking measurements:

First, make sure you have your PAR meter on hand and it’s in good working condition. Ensure that it’s clean and free from any dirt or damage.

PAR meters need to be accurate to provide meaningful data. To achieve this accuracy, follow the instructions that came with your PAR meter carefully.

Calibration is like teaching your meter how to measure light correctly. It’s similar to checking that a scale shows the right weight before you use it. By calibrating your PAR meter, you ensure that the readings it gives you are as precise as possible.

Place your PAR meter near the area of your aquarium where you intend to measure the light. Make sure it’s properly positioned and ready to take readings.

By getting your PAR meter ready in this way, you guarantee that the measurements you collect will be reliable and accurate, helping you make informed decisions about the lighting conditions in your aquarium for your corals’ well-being.

Step 3: Measure Light at Different Depths

Now that your PAR meter is ready, it’s time to gather data about the light in your aquarium:

Take your calibrated PAR meter, the device that measures light, and turn it on. Make sure it’s working correctly and displaying readings.

Start measuring the amount of light in your aquarium. To do this, move your PAR meter to different levels within your tank. Pay special attention to the spots where you’ve placed your corals. These are the areas that need the right amount of light for their health.

As you take measurements at different depths, write down the numbers your PAR meter shows. By measuring at various depths, you get a better picture of how light is distributed in your aquarium, especially where it matters most for your corals.

Step 4: Record Your Measurements

Now that you’re taking light measurements in your aquarium, it’s important to keep track of the data you collect:

As your PAR meter displays numbers indicating the amount of light, jot down these numbers. It’s like taking notes in a class.

Remember to write down where you took each measurement within your aquarium. For example, if you measured light near a certain coral or at the front or back of the tank, make a note of it.

This helps you remember where you checked the light intensity. Also, write down how deep you measured the light. This information is vital because different corals might need specific amounts of light at different depths.

By recording your measurements, you’re essentially creating a “light map” of your aquarium. This map will be a valuable tool for making informed decisions about your coral’s lighting needs in the next steps. It’s like keeping a diary of your aquarium’s lighting conditions.

Step 5: Analyze Your Data

Now that you’ve gathered measurements and recorded them, it’s time to make sense of the information you’ve collected:

Take a close look at the numbers you wrote down from your PAR meter readings. You’re essentially studying the “light report” you created for your aquarium. Try to find similarities or trends in your data. Are there areas where the light is consistently bright or dim?

Look for patterns in how the light changes at different depths and locations in your aquarium. Pay attention to any significant differences in light levels. Are there places where the light is too strong or too weak compared to what your corals need?

Identify spots where adjustments might be necessary. Based on your analysis, you’ll be better equipped to make decisions about your aquarium’s lighting.

You might need to adjust the lighting schedule, intensity, or position of your lights to create the ideal conditions for your corals.

Step 6: Make Necessary Adjustments

Now that you’ve gathered and analyzed your data, it’s time to use that information to create the perfect lighting environment for your corals:

Take a close look at your data and observations. Ask yourself if any areas in your aquarium are getting too much light or not enough light for your corals to grow happily.

If your data shows that some areas get too much light, you can adjust the schedule. This means you might make the lights turn on or off at different times.

For places with too little light, you can increase the time the lights are on. If the data suggests that the light is too strong or too weak in certain areas, you can change the intensity of the lights.

Your goal is to create the best possible lighting conditions for your corals. Each type of coral has specific light requirements, so tailor the light to their needs.

By following these steps and making the necessary adjustments, you’re essentially becoming a “light manager” for your aquarium. 

You’re ensuring that your corals get just the right amount of light they need to thrive and be happy in their underwater home. This careful attention to their needs will help them grow beautifully in your aquarium.


In summary, becoming skilled at measuring PAR is crucial for making your reef tank a success. By having the right information and tools, you can make sure your corals get just the right amount of light they need to grow beautifully. 

So, jump into the world of PAR measurement, light up your reef, and witness your underwater garden flourishing in all its stunning beauty. Your hard work will be repaid with a captivating underwater paradise that amazes everyone who sees it.


How can you check PAR without a meter? 

You can get a rough idea of PAR without a fancy meter by looking at your plants. If they’re growing well and are healthy, it usually means they’re getting enough light.

You can also compare your lighting setup to the recommended guidelines for your type of plants.

Can a phone measure PAR? 

Typically, regular smartphones can’t directly measure PAR accurately. However, some apps claim to estimate light levels using your phone’s camera, but they may not be very precise. It’s usually better to use a dedicated PAR meter for accurate readings.

What is the minimum PAR for flowering? 

The minimum PAR (light intensity) needed for flowering varies depending on the type of plant. In general, most flowering plants require a PAR of around 200 to 400 micromoles per square meter per second (µmol/m²/s) for healthy flowering.

However, some plants may need more light, so it’s best to research the specific requirements of your plant species.

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