Many reef aquarists looking to upgrade or modify their lighting system ask about T-5 fluorescent bulbs.
If all you’ve heard about is LED fixtures, you may think T-5s are old-fashioned or outdated.
It’s true T-5s have been around for a long time. They were first introduced to the market in 1995.
But they’re still an excellent source of PAR for growing corals and a favorite among serious reef enthusiasts.
Let’s take a look at the t-5 technology.
In this article
What’s a T-5 bulb?
There are a variety of fluorescent light bulb sizes. Many modern aquarium lights are now using the T-5 bulb.
The “T” stands for “tube.” Not all fluorescent bulbs are straight tubes, so the “T” is important as a specification.
The number 5 represents the diameter of the tube. The number 5 means the tube is 5/8 inches (16 mm) in diameter.
What About T-8 Bulbs?
The T-8 bulbs are 1-ich (26-mm) inches in diameter.
Standard T-8 bulbs come in longer sizes than T-5 bulbs. T-8 and T-5 bulbs cannot be used on the same fixture.
T-8s have a “medium” bi-pin base on each end. T-5s use the “miniature” bi-pin style base.
T-5 Regular and High-Output Styles
The bulbs are available in standard output and high output. The wattages for standard T-5 lamps are 14, 21, 28, and 35 watts.
The high-output T-5 bulbs are designated HO (high output) and are available in 24, 39, 54, and 80 watts.
Using T-5 Lighting with Corals
T-5 lighting continues to be popular with reef keepers because they are very simple to set up and use.
Long before LED fixtures became available, reefers were fragging and raising SPS corals under T-5 lighting.
By selecting a combination of reef-designed T-5 bulbs, you know you’re getting the right PAR for your SPS corals.
Many LED users say they have to adjust the color and output of their LED fixtures.
With T-5s you just turn on the fixture, and your corals will be bathed with the proper light spectrum.
T-5 bulbs don’t create “hot spots” like some LED fixtures.
Sometimes even the best LED fixtures create a super-bright spot over a small section of the reef. This can be too intense for many corals. T-5 fixtures don’t have this issue.
Retrofitting with T-5 Bulbs
If you’ve got an older light fixture, you can often make the switch to T-5s with a retrofit kit.
The kits come with an electronic ballast, wiring, end caps and a special reflector. Simply remove the old ballast and end caps and attach the new system on the existing fixture.
T-5 Reef Lighting Fixtures
Your best bet is to go with a modern T-5 light fixture. Older fixtures are made of plastic, which can become brittle with age. A new T-5 fixture will last for years, many made of lightweight aluminum.
We’ll review several of the best T-5 reef lights later in this article.
Tips for Using T-5 Lighting
T-5 lighting is one of the easiest methods of lighting a reef aquarium.
The deeper the aquarium, the more light you’ll need. That’s why you may find T-5 lighting fixtures of the same lengths but some will have more bulbs.
Simple fixtures sit on top of the tank. Larger T-5 systems are hung above the aquarium.
When hanging the fixture, raise it high enough so that there is a little light spill around the edges of the aquarium. This ensures light is reaching all corners of the aquarium.
You can also mix and match T-5 bulbs in the same fixture. This allows you to tailor the light color and PAR to satisfy your reef tank’s needs.
Don’t Forget to Change T-5 Bulbs
T-5 bulbs slowly degrade, losing their spectral qualities. It is recommended to replace the bulbs every 12 to 18 months.
Old bulbs still light up but the output and quality decline. You should not replace all of the bulbs at once as this sudden rise in intensity tends to shock the corals.
Some aquarists claim their corals were “burned” when they swapped out all the bulbs at once.
Set up a replacement schedule where you replace one bulb each month until they’re all replaced with new tubes. This allows the corals to adapt back to the full intensity of the bulbs.
Keep the Bulbs Clean
Salt spray on the light fixture and clear panel will reduce the light reaching the corals. Salt will also corrode many metals used in the switches and end caps.
If your bulbs are exposed to salt spray, periodically wipe them down with DI water and a soft cloth. Allow the bulbs to cool before touching them with a damp cloth.
T-5 Lighting Review
There is a T-5 light for just about any size reef aquarium. We’ve rounded up some favorite models and listed their features and benefits.
Be sure to note the length and number of bulbs when comparing models. Some smaller lights mount on top of the aquarium, while others are designed to be suspended above the tank.
1. ATI SunPower T5 HO Fixture
ATI is known for producing high-end T-5 aquarium lights. This 48-inch-long fixture holds 8 54-watt bulbs.
This is ideal for a deep aquarium or for suspending above a wide, open-top tank.
Each bulb has its own individual parabolic-style reflector. The German-made reflector is like a mirror, reflecting light down into the aquarium.
The fixture uses three cooling fans to keep things cool.
The light comes with a hanging kit. The light is recommended for mixed reef aquariums up to 175 gallons (650 l).
ATI also manufactures the Powermodule T5 / LED Hybrid Light which combines T-5 bulbs with LED lighting.
The Aquatic Life X18 Hybrid fixture makes it easy for you to combine your preferred LED fixture with T-5 HO fluorescent lighting.
You’ll be able to use a LED fixture with this non-dimmable T-5 lighting system.
The system works with major LED brands, including Aqua Illumination Hydra 26 & Hydra 52, EcoTech Radion XR15w & XR30w, Kessil A360X, A360WE, AP700TM and others.
The light holds four 60-inch (150 cm) HO bulbs. It comes with a ballast, silicone end caps and suspension cables.
3. Coralife Aqualight Dual T5 High Output Fixture
The Aqualight High Output T5 Dual Lamp Fixtures come complete with two high-output bulbs. Each high-output lamp provides approximately twice the light output of a traditional T8.
The Coralife Aqualight comes with 10,000K and Actinic lamps, making it ideal for saltwater and reef aquariums and also frag tanks.
The bulbs are protected with an acrylic splash guard. The housing is made of rust-free aluminum.
The Aqualight has adjustable legs for mounting it on the lip of the aquarium.
This model is available in 20″ 24″ 30″ 36″ and 48″ lengths.
4. Wavepoint HO T-5 Lighting
The Wavepoint two-bulb HO T-5 fixture is perfect for smaller reef tanks with corals. The small, compact design includes many of the features found on larger lights.
The Wavepoint uses a sealed glass splash guard to keep moisture out while allowing full light transparency.
Each bulb has a mirror-like parabolic reflector to aim PAR directly into the tank.
The aluminum fixture is resistant to corrosion and moisture. The light features a UL-approved GFIC power plug for extra safety.
The Wavepoint sits on the upper edge of the aquarium on legs. This two-bulb system includes 1 SUN WAVE Lamp & 1 SUPERBLUE 460 Lamp.
This light needs no cooling fan. It is available in 24”, 36” and 48” lengths.
5. Hamilton 48” Fiji Sun
Hamilton has been producing aquarium lights for over 30 years. The Fuji Sun allows you to use daylight and actinic bulbs in your preferred combination.
The light comes with two German-made 54w Actinic Blue T5 HO and two German-made 54w 10000K Ice White T5 HO bulbs.
This makes the Fuji Sun reef-ready for keeping SPS and other corals.
The fixture has a low profile and is lightweight. This model uses a quiet cooling fan. The mirrored parabolic reflectors keep the light in your tank.
You can suspend the fixture from the ceiling with the adjustable stainless steel cable system or mount it directly on top of your aquarium with the legs.
This fixture is a popular choice for 55-gallon (200 l) reef aquariums.
6. Reef Brite Supra Slim Line Dual T5 Retrofit Fixture
The Reef bright retrofit system is a simple way to swap out your old, inefficient bulbs and ballast with a new HO T-5 lighting system.
The Slim Line system is designed to fit into any tank with a canopy. The Slim Line fixtures pack the bulbs tightly together, allowing you to install them in locations where traditional kits won’t work.
In some cases, multiple retrofit units can be placed in the hood, creating a 4 or even 6- bulb fixture.
The kit does not include bulbs, but you can select your favorite combination of tubes. The retrofit kits are available in 24”, 36” 48” and 60” lengths.
Each fixture holds two bulbs. You can also add one or more LED strips if you desire. The kit comes with reflectors, end caps and an electronic ballast.
One of the main considerations is determining how much lighting your reef aquarium needs. Too much light stresses corals and reduces their growth.
If you’ve got a large frag tank or display reef, the ATI Sunpower fixtures have the PAR and penetration power you’re looking for.
The Hamilton Fuji Sun pairs well with a 55-gallon (200 l) reef tank.
For smaller nano and AIO systems consider the Coralife Aqualight or Wavepoint fixtures. They’ll provide plenty of light and sit right on top of your aquarium.
If your goal is a T-5 retrofit, the Reef Brite Supra Slim kits are ideal. You can run all T-5s or add LED strips as an option.
Aquatic Life X18 Hybrid makes it easy to add T-5 lighting with today’s popular LED fixtures. If you own LED lights and want to add T-5 lighting, this system is the way to go.
If you have any questions or comments, please leave them below.