A pink-weighted T8 tube. The spectrum is shifted towards red and violet, which makes the reds and blues on tropical fish look far stronger than they do under a daylight tube, and pushes plant growth along. The trade-off is honest: it is a flattering light, not a neutral one, so a tank lit only by pink tubes reads warm. Most people pair one with a daylight tube rather than running pink alone.
Sizes
- 33cm — 10w
- 45cm — 15w
- 60cm — 18w
- 75cm — 25w
- 90cm — 30w
- 120cm — 36w
- 150cm — 58w
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.