Actinic blue in the T5 format, for marine and reef tanks. T5 delivers noticeably more output than the same length in T8, which matters on a reef where the light has to reach the bottom of a deeper tank. As with any actinic, this is a supplement rather than a complete lighting solution — pair it with a daylight tube unless you specifically want a blue-only look.
Sizes
- 212mm — 6w
- 288mm — 8w
- 397mm — 16w
- 550mm — 24w
- 850mm — 39w
- 1150mm — 54w
Match the wattage, not only the length. The tube has to suit the ballast or transformer already in the fitting, and length alone will not tell you that — read the wattage printed on the tube you are taking out.
Replace them about once a year. Fluorescent output and colour shift long before a tube actually fails. One that still lights can be doing well under half the work it did when new, and plants notice before you do.
Run the light on a timer. Six to eight hours a day is a sensible starting point, and consistency matters more than duration.