The Talkingreef Community FAQ

T5 is simply a collective term for a narrow-diameter fluorescent light tube. Standard 1" fluorescent tubes are called T8s, and are used everwhere as normal fluro's, T12 are mainly used for industrial applications.
T5s are 5/8th of an inch in diameter & run from a special ballast, similar (but different) to the type used for standard fluorescent bulbs.

The makers claim that certain T5s are roughly three to four times more effective than a standard fluorescent bulb of similar wattage. Therefore, they're being marketed as a replacement for the large banks of standard fluorescents that people used to use over their reef tanks. By using T5s you'll be able to use fewer tubes than before, and squeeze much more light power under your hood.

Well here is what they mean
NO = Normal output
HO = High output
VHO =Very high output
Which in turn need specific power rated ballist to power them. but doesn't specifically indicate one is better than the other

Yes, T5s produce a "flatter" light, like that produced by a standard fluorescent, rather than an intense directed spot of light like a metal halide. The light levels throughout the tank are more uniform, but you don't get the natural-looking rippling light effect on your substrate you get from a metal halide. Some reefkeepers reckon they lack the "punch" of metal halides for penetrating deep water, so many use a combination of the two types together. Compared to a standard fluorescent, they're considerably brighter to look at.

They appear to work well and are fast becoming very popular with modern reefers. Experts reckon the light produced may not quite match that of metal halides but can still be sufficient to get decent coral growth, even in the more demanding stony corals. However, in very deep tanks you might need to confine the light-loving corals towards the upper layers of the tank to ensure they get plenty of light.

Fluorescents like T5s get very warm but the makers claim that they "don't give off radiant heat", so they're less likely to overheat the aquarium than halides. However, they still get almost hot enough to fry an egg on, so they must have more effect upon water temperature than the producers claim. Some can be installed within the hood, so they're handy if space is limited, or if you're unable (or unwilling) to suspend a luminaire from your ceiling.

T5 bulbs should last for up to 15000 hours with only a 20% drop off in output. This works out at about 1250 days (more than three years) based on a 12-hour photoperiod. This is far longer than either metal halide or standard fluorescent lamps. The thing to keep in mind is virtually every bulb eventually deteriorates and the same applys to T5s.

The number and combination of bulbs you add largely depends on what you are keeping. You'll probably be looking at four to six for a 75 gallon tank, but you might get away with less if you're keeping inverts that are tolerant of lower light levels, such as zoanthids, Pachyclavularia, Leather corals and corallimorphs (mushroom anemones). It is estimated that three 54w T5s as a replacement or compare to each 150-175w metal halide.

The cost of the units are slightly cheaper, the main saving is in the costs of replacement bulbs & overal running costs. T5s produce more light watt-for-watt than standard so they should save alot in the long run!

There are differences in the types of ballast used, which may have some bearing on performance, as well as minor differences in the build quality of the actual light unit itself.
However, the most critical differences are in the quality and design of the bulb and reflector used.

The phosphor mix in the tube is what makes up the spectra & is designed specifically for use on aquaria. It's a good idea to use a mixture of bulbs to get the spectrum and light quality you're after for the keeping of your specific animals.