• 10,000 K colour temperature — crisp white with a blue bias. This is the reference point most marine photography and most reef tanks are set to, so the tank looks the way people expect a saltwater tank to look.
• Marine and freshwater — Zoo Med lists the lamp for both, and states it supports aquatic plant growth as well as the zooxanthellae in photosynthetic corals.
• 25 watts over 36 inches — Zoo Med's imperial T8 range tops out at 25 W in this length, so one tube carries a hood rather than needing a pair to look bright.
• Effective to 10,000 hours — Zoo Med's published rating, and the figure to replace on. Output drops away well before a fluorescent tube stops lighting.
• Made in Europe — Zoo Med states the lamp is manufactured to premium standards in Europe.
• Runs solo or paired — unlike an actinic, a 10,000 K daylight tube is a complete viewing light on its own, and pairs with actinic when you want more blue.

Zoo Med builds three aquarium T8 lamps around three different jobs. They are not upgrades of one another.

In a two-tube 36 inch hood, Ocean Sun plus Coral Sun Actinic 420 is the standard marine pairing. Ocean Sun plus Ultra Sun gives a brighter, more colour-accurate freshwater result.

Match the tube to the lamp holders in your fixture, not to the length of the tank. All five lengths share the 10,000 K output.

This is the 36 inch, 25 watt imperial lamp, Zoo Med item OL-36. Confirm your fixture is rated for a 25 W T8 tube.

Zoo Med runs a second, international T8 range sized in millimetres, in which the closest lamp is the 900 mm OL-36E at 30 W. A 900 mm 30 W fixture and a 36 inch 25 W lamp are not a guaranteed match.

Lamps and ballasts are paired by wattage. A mismatch shows up as short lamp life, flicker, or a tube that will not strike.

If you do not know what your hood is rated for, the tube it shipped with is the most reliable answer.

Zoo Med publishes colour temperature, wattage and rated life for the T8 range, but no PAR or PPFD figures at any depth. We will not estimate them, because an estimate is indistinguishable from a measurement once it is printed on a page.

For a fish-only or lightly planted tank that gap does not matter much — you are buying a viewing light. For a coral tank it matters a great deal, and the honest advice is to buy a fixture that publishes a PAR map, such as the Red Sea ReefLED 50.

Suitable for

• Marine fish-only and FOWLR aquariums running 36 inch T8 hoods
• Freshwater tanks where you want a cool, crisp look rather than a warm one
• Replacing a tired 10,000 K tube in an existing two-tube marine fixture
• Pairing with an actinic tube for a deeper blue overall cast

Not suitable for

• Being the sole light over a demanding coral display — a 25 W T8 is not a modern reef fixture and has no published PAR data
• Fixtures specified for a 900 mm 30 W tube, unless you have confirmed a 25 W lamp will run in them
• T5 and T12 fittings, which use different lamp holders
• Keepers who want warm, natural-daylight colour rendition. At 10,000 K reds are muted; the 6,500 K Ultra Sun with its CRI of 98 is the better choice there
• Planted tanks chasing maximum growth. Zoo Med states it supports plant growth, but 10,000 K is a viewing choice more than a growing one

Replace on hours run rather than on failure. Zoo Med's 10,000 hour rating works out to roughly two years and nine months at a 10 hour daily photoperiod, or about three years and five months at 8 hours. Those are arithmetic on Zoo Med's figure, not separate claims.

A 10,000 K tube shifts visibly as it ages — the blue drains out and the tank starts to look yellow. If you have been meaning to replace it, that colour drift is the cue.

Clean salt creep off the glass when the tube is cool. This lamp contains mercury and must not go into household waste, so take spent tubes to a fluorescent lamp recycling drop-off. Zoo Med refers customers to lamprecycle.org.

It is 91 cm of thin glass. Inspect it for cracks before fitting.

This lamp draws 25 W. At a 10 hour daily photoperiod that is about 91 kWh a year, and at 8 hours a day about 73 kWh. Both are arithmetic on the wattage, so scale them to your own photoperiod and electricity tariff.

• Zoo Med Coral Sun Actinic 420 T8 36 inch — the actinic partner. Pairing 10,000 K with 420 nm actinic in a two-tube hood is what both lamps are designed around.
• Zoo Med Ultra Sun Trichromatic T8 — swap to 6,500 K, or run one of each, if muted reds under 10,000 K bother you.
• Red Sea ReefLED 50 — where to go if the tank becomes coral-driven and you need published output at depth.
• Browse the full Zoo Med range for the other Ocean Sun lengths and the rest of the aquarium T8 lamps.

Zoo Med publishes a one year warranty on this lamp. It applies in addition to your rights under the Australian Consumer Law and does not limit them.

Gradual dimming and colour shift across the rated life are normal for a fluorescent lamp and are not a fault. A tube that will not strike from new is what the warranty covers.

What does a 10,000 K aquarium tube look like?

10,000 K reads as crisp white with a distinct blue bias — cooler than daylight, without being blue like an actinic. It is the standard look for marine tanks and gives water depth and a slightly shimmering quality. Warm colours, particularly reds, are muted compared with a 6,500 K daylight lamp.

Can the Zoo Med Ocean Sun be used in a freshwater aquarium?

Yes. Zoo Med lists the Ocean Sun 10,000 K for both marine and freshwater aquariums and states it supports aquatic plant growth. It gives freshwater tanks a cooler, cleaner look than a standard warm-white tube, though a planted tank chasing growth and colour accuracy is usually better served by the 6,500 K Ultra Sun.

What is the difference between Ocean Sun and Ultra Sun?

Ocean Sun is a 10,000 K lamp built for the cool blue-white look of a marine tank. Ultra Sun is a 6,500 K trichromatic daylight lamp with a CRI of 98, built for colour accuracy and planted freshwater. Both run on their own, so the choice is about the look you want rather than which is brighter.

What wattage is the 36 inch Ocean Sun?

The 36 inch Ocean Sun is 25 watts, listed by Zoo Med as item OL-36. Zoo Med's separate international range is sized in millimetres, where the 900 mm OL-36E is 30 watts. Check which one your fixture is rated for before ordering, as lamps and ballasts are matched by wattage.

How do I dispose of a used aquarium fluorescent tube in Australia?

Fluorescent tubes contain mercury and should not go into household waste. Take spent tubes to a lamp recycling drop-off point — many council waste facilities and lighting retailers accept them. Zoo Med refers customers to lamprecycle.org for disposal guidance.