Email Sign Up
View Cart Home About Us Policies Contact Us
Aquarium Aeration
Air Pumps
Air Stones
Airline Tubing
Airline Valves
Aquariums & Fish Tanks
Aquarium Kits
Fish Bowls
Breeders & Hatcheries
Coral Mounts & Tools
Aquarium Accessories
Aquarium Backgrounds
Aquarium Chillers
Aquarium Filters
Power Filters
Bio Wheel Filters
Canister Filters
Internal Filters
Undergravel Filters
Sponge Filters
Diatom Filters
Fluidized Bed Filters
Wet/Dry Filters
Aquarium Filter Accessories
Filter Bags
Filter Cartridges
Filter Media
Filter Parts
Fish Food & Feeders
Fish Food By Brand
Fish Food by Type
Fish Feeders
Aquarium Gravel & Substrates
Aquarium Gravel
Aquarium Sand
Aquarium Health
Vitamins & Supplements
Stress Relief
Dosing Equipment
Aquarium Heaters
Shop By Brand
Submersible Heaters
In-Line Heaters
Aquarium Lighting
Lighting Fixtures
Light Bulbs
Hoods & Canopies
Lighting Accessories
Aquarium Maintenance
Cleaning Supplies
Aquarium Nets
Putty & Sealants
Pest Control
Testing Equipment
Aquarium Ornaments
Artificial Plants
Genuine Driftwood
Aquarium Ornaments
Aquarium Decorations
LED Accent Lighting
Aquarium Parts
Shop by Type
Shop By Brand
Aquarium Plant Care
Plant Food & Supplements
Plant Substrates
CO2 Systems
Protein Skimmers
Venturi & Beckett
Turbo Driven
Protein Skimmer Parts
Aquarium Pumps & Power Heads
Power Heads
Water Pumps
Wave Makers
Aquarium Reactors
Aquarium Salt
Freshwater Salt
Marine Salt & Reef Salt
Special Care Products
Brackish & Black Water
Betta Care Products
Cichlid Care Products
Goldfish Care Products
Testing Equipment
Aquarium Test Kits
Hydrometers & Refractometers
Meters & Probes
Water Purification
RO/DI Water Filters
UV Sterilizers
UV Sterilizer Parts
Water Treatments
Conditioners & Additives
Ammonia Removers
Water Clarifiers
Aquarium Resources
Freshwater Aquarium Setup
Aquarium Maintenance
Equipment Guides
Fish Care Guides
Fish Tank Supplies > Fish Tank Resources > Aquarium Equipment Guides > Fish Tank Lighting

Aquarium Lighting

How to choose the best lighting for your tank and viewing pleasure.

Author: Aaron Hill


Not that long ago, I started my first real venture into setting up a healthy saltwater aquarium. I knew from the start that it was going to be a long term goal and that I would need to do a lot of research and planning.

In this article I will explain some of the basic things you need to know when planning aquarium lighting for any tank, be it saltwater, freshwater, fish-only, reef or planted. Basics like the color spectrum, the various types of bulbs available, and what situations call for what types of lighting. There are a lot of choices, and choosing shouldn't be mysterious or confusing. Once you understand the basic concepts, you'll be well on your way to aquarium success!


When it comes to setting up a successful aquarium, there are a number of decisions to make in advance - tank size, filtration, circulation, and lighting being the most essential. These decisions directly impact your success. They'll be determined by how many and what type of organisms you want to keep, so the first step in your planning is to do a little research on the fishes, invertebrates and plants that interest you to see if they have special needs. Planning ahead before purchasing equipment helps you avoid unexpected expenses down the line!

Your goal in aquarium lighting is to recreate the natural habitat of your organisms. The most basic thing to consider is the day/night cycle. It may seem simple, but many beginning hobbyists don't understand how important it is. You'd be stressed out if you had to live under bright lights - or very little/no light - for 24 hours a day, every day. It stresses fish and other creatures too, causing poor health and interrupting natural cycles of behavior. Since your aquarium will not experience day and night normally inside your house, you will have to create them!

First, daylight. Lighting not intended for aquariums lacks wavelengths of the daylight spectrum important to the health your organisms, while including wavelengths that promote algae growth. Placing your tank in direct sunlight seems logical, but causes overheating, accelerated algae growth and a host of related problems. So you will have to plan lighting just for your aquarium, unless you have a kit or hood with lights built in. This article will deal with choosing the correct daylight simulations for your aquarium community.

That said, don't forget about night - about 12 hours of it! Most natural environments - especially the open ocean - are rarely pitch black at night, but lit by low-intensity moonlight. Inexpensive lunar LEDs are the best source of night lighting, and many fixtures include them. They provide illumination for observing nocturnal behavior without disturbing resting organisms, and make your aquarium function as a cool night light - they may also promote good health and natural behaviors like spawning. There isn't much to choosing lunar lights, so we won't be going into it here, but you can find more information on forums and other sites online.

In summary, plan your lighting in terms of daylight and moonlight. Proper day/night cycles provide the best conditions for a thriving aquarium, and you should strive to provide them. (It's a great idea to use a lighting timer so you don't forget, or if you can't be there). Determining what type of day lighting your organisms need will be the basis of your decisions, so read on!

Determining what lighting you need

The type and intensity of lighting in an aquarium affects health, stress, coloration, photosynthesis, and stimulates reproduction, among other things.

Some aquarium organisms come from shaded regions, like rain forest rivers, where most of the light in their day is indirect. These organisms do not require intense day lighting and some even fare poorly if subjected to it (e.g. mushroom anemones). These types of organisms may not need a full 12 hours of daylight.

Then there are high light organisms. These guys tend to come from shallow tropical areas where water clarity is sublime and they are bathed with intense, full spectrum lighting from the sun for 12 hours a day. These organisms have adapted to these conditions and some do not just flourish best under intense lighting, but require it to live (e.g. Tridacna Clams). Most coral reefs grow in shallow waters like this. Aquatic plants need intense lighting as well.

"Actinic light" is important to reef organisms and deep water fishes. Actinic lights produce UV wavelengths at the blue end of the daylight spectrum, which penetrates water the furthest and is most easily absorbed by corals and invertebrates. It is crucial to corals that rely on symbiotic algae (Zooxanthellae) that use UV light for photosynthesis. Actinic lights are not very intense and appear blue, so actinic fixtures also include daylight spectrum lighting.

Kelvin Ratings

Kelvin ratings (K) measure the color temperature of light. So far we've talked a lot about intensity, so why does color matter? The full spectrum of light produced by the sun consists of many different wavelengths - combined they appear white or yellowish depending on time of day, but individually they have distinct colors. You'll see numbers like 5500K, 6500K, 10,000K, and 20,000K when looking at aquarium lighting. These ratings refer to the color spectrum the lamp emits. Intensity on the other hand is partly determined by wattage, but there's no easy rule to follow there as different types and brands of bulbs differ in intensity even with the same wattage.)

You won't see aquarium lamps rated below 5500K (except for incandescent bulbs, which are not expressly for aquarium use), as these red/yellow wavelengths promote algae growth. Lamps rated at 5500-6500K are generally appropriate for freshwater tanks unless they are quite deep (the more water your light must penetrate, the less intense it will be when it reaches your organisms). If necessary, they can work for saltwater or low-light reef tanks if supplemented with actinic light to provide the blue end of the spectrum that they lack.

A 10,000K lamp gives off crisp intense white light with a bluish cast. They are ideal for reefs, deep water fish, and plants. They will really make the colors of your colorful organisms pop. 20,000K lamps are very intense, mostly blue and are really only needed for the deepest tanks and deepest-water fish.

Actinic light is not Kelvin rated, but measured in nanometers (420nm or 460nm) as it refers to the UV spectrum of light which is not completely visible to us. There is some debate in the aquarium community about the best uses for these bulbs. Visually they are blue and can bring out nice colors in tropical fish. Generally they are considered important for reef tanks and you often see them combined with daylight lamps in light fixtures (this produces better viewing than strictly blue light).

50/50 lamps are available in all bulb types except incandescent. These lamps output both daylight spectrum and actinic spectrum at the same time, or output 2 different daylight or actinic spectrum ratings. They can be an excellent choice for reef tanks or deep tanks.

Lunar LED lighting is too low-intensity for Kelvin ratings. Usually it is blue and provides little illumination. There are also white lunar LEDs that mimic full-moon lighting. Either white or blue lunar lights are fine for any tank, but if you're interested in breeding fish you may find you need both to simulate lunar cycles.

Lamp Types

The type of lighting you choose isn't as important as spectrum or intensity, though these factors are related. With some exceptions, lamp or bulb type is up to you and the needs of your budget.

incandescent aquarium bulbs


Incandescent bulbs are the ubiquitous, tungsten filament, screw-in bulbs that are used in homes and lamps. They include halogen lamps. As a general rule they are not calibrated for aquarium use, though they may be sold as aquarium bulbs.

Incandescent bulbs are sometimes used in small fish bowl lamps. They are the cheapest bulb type and the easiest to find, and come in different colors. However their color spectrum is limited to 2700K for normal incandescents and 3000K for halogens, moving towards the red end of the spectrum and giving off a yellowish light. This spectrum promotes algae growth.

They are also the least efficient type of bulb, using a lot of energy and producing a lot of heat compared to the intensity of their output. Because of their high heat output they may be best suited for terrariums housing reptiles. They are not recommended for aquarium use in anything but the smallest setups.

fluorescent aquarium bulbs


Fluorescent lighting is the most common choice among aquarium hobbyists, and fluorescent lamps are typically included in aquarium kits. These are the long round "tubes" that you see in office buildings. They provide light over a larger surface area than smaller bulbs and don't run as hot. They also take up more space and are not as intense as some other types of lamps, even with the same Kelvin ratings.

The great thing about fluorescents is that they are readily available (but stick to those intended for aquariums), and typically the most affordable choice. They are available in a wide range of color spectra and come in 3 different sizes by thickness. T12, T8, and T5. T12 and T8 bulbs are standard and can fit in the same fixtures, but T5 lamps require specific fixtures. The benefit of T5 lamps is that they are shorter - you can fit 8 tubes in the space that 4 T12's occupy, achieving higher intensity in a smaller space.

For deeper tanks, reef tanks and planted tanks, there are special fluorescent lamps that run at higher wattages for intense lighting. These are termed High Output (HO) and Very High Output (VHO) lamps as opposed to Normal Output (NO) lamps. HO and VHO lights require special ballasts and end-caps in order to function and will not work with your standard NO ballast. (Ballasts & end-caps usually come with fixtures.) T12 and T8 lamps are available in both HO and VHO while T5 lamps are only available in NO and HO.

HO and VHO bulbs don't last as long as fluorescent bulbs, and VHO fixtures are difficult to find. Some aquarists feel that VHO is more trouble than it's worth, and if you think you need VHO bulbs you are better off going with power compacts.

power compact aquarium bulbs

Power Compact Fluorescents(PC)

Power compact (PC) bulbs, better known as compact fluorescents, are the new technology in fluorescents and fast replacing the popular VHO Fluorescent systems over many reef aquariums. They take up less space than NO fluorescent bulbs and use less power to produce more intensity.

These lamps require special fixtures and will not work with your standard fluorescent light fixtures or ballasts. You can buy complete fixtures, or retro-fit kits that come with the reflector, ballast, end-caps, and most often the bulbs as well. All that is needed is for you to install them into your hood (which may only fit a certain type of light, but you can often custom rig them) or over your canopy.

PC bulbs come in twin- and quad-tube designs and are available in almost all the same color temps as other lamps. PCs are available in two different configurations: Straight-pin, and Square-pin (shown above). Both have 4 pins but either straight across or two stacked on two, and they cannot be interchanged. Make sure you buy appropriate replacements of your fixture.

metal halide aquarium bulbs
Metal Halide

Metal Halide lamps are basically HIDs for your fish tank. They produce the most intense lighting available. They are highly prized for their unique ability to create a "shimmering light" effect in the aquarium that mimics sparkling sunlight in a shallow reef, and are primarily used in saltwater reef tanks where light hungry corals, anemones, and clams are kept. They are not generally recommended for beginners to the hobby for several reasons.

Metal Halide lamps are high-powered bulbs that require special ballasts and fixtures. Bulbs and fixtures are more expensive than every other type of lighting, but you can't beat them for intensity. They range in wattages from 70W and all the way up to 1,000W in a single bulb! Each wattage requires a compatible ballast.

Unlike fluorescent lamps, which spread light out over the entire length of the bulb, metal halides are a pinpoint source of light. This means that all the heat generated by the bulb is centralized in one spot as well. These bulbs get HOT, and you should NEVER handle a bulb that is on or has not been turned off for less than an hour. You should also avoid ever touching the bulb, hot or cold, directly with your fingers, which gets oil on the lamp, weakening the glass.

Because of the intense heat generated by these bulbs, most fixtures include cooling fans and mount at a distance above the water's surface to avoid overheating your tank. A single metal halide bulb lights an area of about 4 square feet, so in a 4' tank you would need 2 Halides to cover the whole length of the aquarium. Fixtures will include appropriate bulbs for the length they cover.

Halides are either single-ended (pictured above), (aka mogul base, or screw socket) or double-ended (pictured below), (aka HQI).
HQI aquarium bulbs
HQI Halides

HQI Halides are usually the ones that are included in combination fixtures along with Power Compacts. Unlike single-ended lamps, they do not have a filtering mechanism to block short-wave Ultra-Violet light that is emitted by these powerful lights. It is therefore necessary to make sure there is a sheet of glass or plastic in between the bulb and the tank to filter this UV out (most fixtures will include this).

You can get sunburn from unshielded metal halide lamps if your skin is exposed to them for a length of time. Halides in general come in just about the same color temps as any other bulb, but are most often found between 10,000K and 20,000K.

Choosing the right light for your setup

Now that we know what we're dealing with in the world of aquarium lighting, we can make things pretty simple. Most freshwater aquarium fishes do well under any color spectrum range of aquarium lighting from 5500K to 10000K and are largely indifferent to the type of lamp you use.

Plants can survive with only a little more light than a fish-only tank, but benefit greatly from higher intensity. Saltwater Corals, Anemones, and Clams require intense lighting in the aquarium to maintain their symbiotic algae, known as Zooxanthellae. Special lighting is necessary to keep light sensitive coral and plants as healthy as possible.

Now to choose!

Bulb Type Color Spectrum Intensity Ideal Livestock Pros Cons
Incandescent/Halogen 2700-3000k, no actinic Lowest Bowls with low-light organisms, reptile terrariums Cheapest, easy to find, different colors. Poor spectrum, encourage algae, high heat/inefficient
Normal Output (NO) Fluorescent 5500-10000K & actinic Low Freshwater fish only, shallow tanks Cheap to buy & replace, easy to find, many different types/colors/effects. Large bulbs. Might not penetrate deep water.
High Output (HO) or Very High Output (VHO) Fluorescent 5500-10000K & actinic Moderate-High Freshwater planted, nano reefs, saltwater fish only Smaller & Brighter than fluorescents Need specific fixture, won't last as long as NO bulbs.
Power Compact (PC) Fluorescent 5500-10000K & actinic Moderate-High Anything Moderately priced, versatile, long lasting, smallest fluorescent bulb More expensive than fluorescents
Metal Halide & HQI 5500-20000K & actinic Highest Coral reefs, high light organisms, best for plants Best for deep tanks and light lovers Expensive to buy and replace

Here are some commonly used general guidelines for planning:

  • Fish-only tanks: minimum of 2-3 watts per every gallon of tank water. Anything deeper than 20" benefits from actinic supplementation.
  • Planted tanks: minimum of 4 watts per gallon. The more the better.
  • Reef Tanks: minimum of 4-6 watts per gallon, and 8-12 or more watts per gallon for tanks containing Coral, Anemones, or Clams.
Kelvin Rating:
  • Fish: 5,500K to 20,000K depending on the species. Deeper tanks need actinics, especially saltwater tanks.
  • Plants: 6,500K to 18,000K.
  • Reefs: 9,000K to 20,000K with Actinics, and depending on the particular organisms.
  • 10,000K lights are the all-around safest choice for any tank. These lights provide an excellent crisp bright white that looks amazing. Most aquarium owners I have talked to feel this is the best choice for viewing.
  • Choosing an aquarium background that compliments the colors of your organisms under your lighting gives a nice personal touch.
  • Remember to always research your intended inhabitants to learn what spectrum ranges have the best effect!

In Closing

Hopefully you feel better prepared to choose lighting for your aquarium. Although there are a few basic factors to consider, it's really not as complicated as it may seem at first. There are a number of choices you could make for any tank that will work just fine.

Remember to include a source of night lighting for most organisms, and at the very least turn your daylight lamp off at night (or have a lighting timer do it for you).

It's also a good idea to stick with established brands of aquarium lighting (a good rule of thumb for all aquarium equipment) - you might pay a little more up front, but you are buying additional testing, research, and peace of mind, and you'll save yourself money and effort further down the road.

This may be obvious, but don't forget to match the length of your light fixture to the length of your tank!

There are tons of helpful sites on the internet that offer further information on aquarium lighting and you can always ask around on one of the many aquarium forums for help from other hobbyists. You can find me at Fish Tank Forums if you would like to further discuss this subject or offer comments on the article. My screen name there is ahill3780 and you can find the site at

We encourage readers who find this information beneficial to share it with friends or other interested parties. Link to this article from your own websites!

Replacement Bulbs

Sales   About Us   Policies   Contact   Site Map   View Cart
Contact Us: Copyright© 2013  Aquarium Guys.  All Rights Reserved.