How to Choose a Reef Tank Light: Start With the Corals

By Roy Torres | Infinity and Beyond Aquatics

The most expensive reef-light mistake is choosing the fixture before choosing the corals.

A light can look impressive in a showroom and still leave the edges of your aquarium underlit, overwhelm a low-light coral, or fail to provide the coverage your growing colonies need. The right choice depends less on the brightest number on the box than on the reef you plan to build.

Start with the corals. Decide what you want to keep, whether your aquarium has enough room for those corals to grow together, and what conditions they require. Then use that information to choose a light with suitable intensity, coverage, controls, mounting, and support.

This guide will help you work through that process—from coral compatibility and care requirements to PAR, coverage, mounting, controls, and total cost—so you can buy lighting for the reef you actually want to keep.

First, decide who’s moving in

Are you picturing a mushroom and zoanthid garden? Flowing hammers and torches? A reef full of branching SPS? Or a little of everything?

Research the individual corals on your wish list before comparing fixtures. Soft coral, LPS, and SPS are useful starting categories, but they don’t tell the whole story. Even within a group, lighting and flow needs can differ.

Write down each coral’s lighting, flow, placement, aggression, and space requirements before you buy. That list becomes your lighting shopping guide: it tells you how many lighting zones you may need, where corals can be placed, and how much usable coverage your fixture must provide.

It also helps you plan the reef as a community rather than a collection of isolated purchases. Before choosing a light, make sure the corals can share the same aquarium.

Some corals are good neighbors. Others choose violence.

A reef tank is a neighborhood, and some residents take property lines very personally.

Corals can compete through direct stings, extended sweeper tentacles, and overgrowth. Some also release chemical compounds into the water that can affect neighboring corals. Welcome to the dawn of chemical warfare, reef edition.

Those are different problems: leaving space helps reduce physical contact, but it doesn’t prevent dissolved compounds from circulating through the aquarium.

Plan for grown colonies, not just the tiny frags you bring home. Secure them so they can’t fall onto one another, research their aggression, and leave room for expansion. Similar names or appearances don’t guarantee that two corals can safely touch.

Tank size matters here because you need room for future growth, separation, and different lighting zones. A coral plan that works in a shallow, wide aquarium may not work in a narrow or deep one.

Get their care needs working together

A great light is one part of coral care. Stony corals also need consistent water chemistry to build their skeletons.

Research salinity, temperature, alkalinity, calcium, magnesium, nutrients, and flow for your intended livestock. Aim for compatible needs and a routine you can maintain. Avoid repeatedly changing conditions to chase a perfect number.

Your reef plan should make sense as a whole before the light becomes the star of the show.

Okay, now the fun part: what is PAR?

PAR stands for photosynthetically active radiation, traditionally the light wavelengths from 400 to 700 nanometers.

When reef keepers say “this spot gets 150 PAR,” they usually mean a meter reading of photosynthetic photon flux density, or PPFD. It measures how many photons in that range reach an area each second.

The useful question is: How much light reaches the coral where it actually lives?

That’s different from how bright the aquarium looks to your eyes or how much electricity the fixture uses.

PAR helps you assess intensity. It doesn’t describe the full spectrum, coverage, or daily exposure, and a bigger reading isn’t automatically better.

How much light do your corals need?

There is no universal PAR target for every reef.

Many soft corals suit lower to moderate light, many LPS suit moderate light, and many SPS need stronger illumination. Treat those as broad tendencies, not instructions for every species.

For example, Tidal Gardens notes that torches need less light than some other corals and warns against exposing Acropora to a sudden increase in intensity. Ask about the conditions your coral was grown under, then use its specific care guidance to plan placement and acclimation.

A mixed reef needs suitable zones for different animals. You don’t need to blast the entire aquarium just because one coral prefers stronger light.

Even coverage is key—just avoid weak spots

Look at length, width, water depth, and rockwork, not just gallons.

One of the biggest things I look for is even, usable coverage. You want the light to reach the areas where you plan to grow corals, without a bright spotlight in the middle and weak, dull areas around the edges.

Even coverage doesn’t mean every inch must have identical PAR. A mixed reef can benefit from intentionally lower-light areas. The goal is suitable light where each coral lives, rather than accidental gaps in coverage.

Mounting height affects both spread and intensity, and growing colonies can eventually shade the corals below them. Depending on your layout, overlapping fixtures or supplemental lighting may help fill gaps; check the resulting coverage before simply adding more power.

Compare PAR maps taken at relevant depths and mounting heights. Check the settings used during testing, too. A measurement just below the surface isn’t a promise of the same reading on your sand bed.

If possible, measure your own aquarium with an appropriate underwater PAR meter. Your rockwork and setup are part of the result.

Use this step-by-step reef-light checklist

Work through this checklist before comparing brands or placing an order.

1. List the corals you want to keep

Write down each coral species or type, along with:

• Preferred light level or PAR range
• Preferred placement
• Flow requirements
• Expected adult size
• Aggression and spacing needs
• Whether it may shade or overgrow neighbors

If you are planning a mixed reef, identify the lowest- and highest-light animals. Those extremes will help define the lighting zones your aquarium needs.

2. Confirm that the corals fit together

Check whether the corals can share your aquarium’s:

• Temperature and salinity
• Alkalinity, calcium, and magnesium levels
• Nutrient range
• Flow pattern
• Available space
• Aggression and chemical-competition risks

Plan for mature colonies, not just frags. Mark where each coral will eventually grow and leave room for separation.

3. Record your actual tank dimensions

Measure the aquarium’s:

• Length
• Front-to-back width
• Water depth
• Distance from the water surface to the intended coral locations
• Rockwork height and major shaded areas

Note whether the tank is shallow and wide, narrow and deep, rimmed or rimless, and whether a canopy or other equipment limits mounting options.

4. Divide the aquarium into lighting zones

Sketch the tank from above and from the side. Mark:

• High-light areas for demanding corals
• Moderate-light areas for LPS and adaptable corals
• Lower-light areas for soft corals or acclimation
• Areas blocked by rockwork
• Areas where colonies may eventually shade one another

This prevents you from choosing a fixture based only on the brightest point.

5. Set a practical PAR target for each zone

Use coral-specific care information to establish a target range for each zone. Treat published numbers as planning guidance, not guarantees.

Ask:

• What PAR does each coral prefer?
• Where will that coral sit at maturity?
• Can the fixture provide that PAR at the actual depth?
• Can it do so without making other zones unsuitable?
• Will the coral need gradual acclimation from its current conditions?

Avoid choosing a light solely because it produces the highest possible PAR.

6. Compare coverage at your tank’s dimensions

For each candidate fixture, review PAR maps or manufacturer data that match your:

• Tank length and width
• Water depth
• Mounting height
• Number of fixtures
• Lens, diffuser, or reflector configuration
• Intended operating intensity

Look for usable PAR across the coral-growing area, not just a strong center reading. Check the edges, corners, sand bed, and areas behind or between rock structures.

If one fixture cannot cover the tank evenly, compare multiple fixtures or supplemental lighting rather than assuming more intensity will solve a coverage problem.

7. Confirm mounting compatibility

Before buying, verify:

• The mount fits your tank’s rim or stand
• The mount can reach the desired position
• The fixture can be installed at the recommended height
• The mount supports the fixture’s weight
• The installation leaves room for maintenance
• The light will not interfere with lids, canopies, plumbing, or other equipment
• The mounting position provides the intended spread and reduces unwanted spill

A fixture that cannot be mounted correctly may not deliver the coverage shown in its specifications.

8. Evaluate controls and acclimation

Decide how much control you actually need. Check whether the fixture offers:

• A dependable daily schedule
• Gradual sunrise and sunset changes, if desired
• Intensity and spectrum adjustments
• A coral-acclimation mode
• Manual override controls
• Reliable app or controller access
• Backup or recovery behavior after a power outage
• Settings that are easy to reproduce after maintenance

Detailed control is useful only if you can set and maintain it consistently. A simpler system may be the better choice if it helps you avoid frequent changes.

9. Calculate the complete purchase price

Compare the total installed cost, not just the fixture price. Add:

• Fixtures
• Mounting arms, brackets, rails, or hanging hardware
• Controllers or control modules
• Power supplies
• Diffusers, lenses, or shades
• Supplemental lighting
• Timers or power-management equipment
• Replacement parts
• Shipping and taxes
• PAR-meter rental or measurement costs, if applicable

Then consider ongoing costs such as electricity, replacement fans or power supplies, warranty coverage, and expected service life.

10. Check support and ownership requirements

Before committing, confirm:

• Warranty length and coverage
• Availability of replacement parts
• Customer-support options
• Software or app support
• Repair or replacement procedures
• Noise and heat considerations
• Whether the fixture has a track record in reef applications

A slightly more expensive light may be the better value if it is easier to mount, measure, control, repair, and support.

11. Verify the final setup before adding corals

After installation:

1. Set the fixture at the intended mounting height.
2. Program a conservative schedule.
3. Measure PAR at planned coral locations if possible.
4. Compare readings with your zone targets.
5. Adjust height, fixture spacing, or intensity before adding sensitive corals.
6. Start acclimation gradually.
7. Observe coral extension, coloration, tissue condition, and behavior.
8. Change one major variable at a time.

Your aquarium’s rockwork and water depth determine the final result, so real measurements are more useful than assumptions based on the box or a showroom display.

What makes one light better for your reef?

Use these questions to compare fixtures:

Brand reputation matters, but choose the specific fixture that fits your needs. A familiar logo alone doesn’t answer the coverage question.

Also think about how you like to run your tank. Do you want a simple preset or detailed control? A light you can set confidently and maintain consistently has real value.

Give corals time to adjust

A new light can change intensity and spectrum even when the aquarium looks similar to you.

Use an acclimation program or make gradual adjustments based on the coral’s previous conditions. Keep your schedule consistent, watch the coral’s response, and avoid changing several settings at once.

You bought the light to support your reef. Give the animals time to settle into it.

Choose the light for the reef you want to keep

My approach is simple: choose your corals, confirm that they can share the aquarium, measure your tank, map their future locations, establish PAR targets, compare coverage, verify mounting and controls, calculate the complete cost, and then shop for lighting.

The right fixture gives your corals suitable, even coverage across the spaces they’ll occupy, with controls and support that work for you. Don’t shop only for the brightest point—shop for the whole reef.

And hopefully, everyone in the neighborhood keeps the chemical warfare to a minimum.

Need help choosing? Contact Infinity and Beyond Aquatics with your tank dimensions, coral wish list, lighting zones, and complete budget. We’ll help you work through the options.