so if i use my 20,000k hqi metal halide it will grow plants ? Im under the impression that plants use the red spectrum of 650nm and not the blue .
The way you guys put it makes me think i can light my tank with a candle or a landing light for aircraft and get growth.
Plants can use a vast range of wave lengths to photosynthesize, you shouldn't be worried about this unless you had lights only emitting in a very narrow wave length range, which is not your case for sure as these lights are not normal in the hobby. I am maybe wrong but it seems you are mixing temperature of light, wavelengths and intensity. Obviously you cannot grow plants with a candle because the intensity is too low. You can try to grow plants with a landing light, but I bet you would be growing algae instead... And all this has nothing to do with the temperature.So, what we mean is:
- lights are done by human beings for human beings (also for other purposes) but most of them emit in the visible spectrum. Another fact is that all the living beings have evolved under the same source of light: the sun. Even if living beings can use different parts of the spectrum, most of them do ok under the visible part of it. This is why any light you can see can somehow be 'seen' by plants
- aquatic plants have evolved under different light conditions: clear water, dark water, sunny position, shade, shallow water, deep water. The light is also different during the day or in different moments of the year. They can use different pigments to get adapted to all this.
- intensity (better measured in PAR, but the classic watts per gallon rule of thumb can also be used sometimes) is far more important than other issues. This is due to the fact that light is not often limited in our tanks (we can buy powerful units) but CO2 efficiency is quite limiting and optimal levels more difficult to achieve (we can buy nice co2 equipment but that doesn't work necessarily ok in our tanks... It is much more complex). This is why Clive mention to better focus on this
- light temperature (measured in K) or light source (led, T5, metal halide, T8, etc.) are different things and not related to plant growth. Light temperature has to do to how your tanks looks like (greenish, bluish, reddish... Chose the one you prefer). The light source is more related with other issues such as consumption, penetration in the water column.
Your pinkish lights will grow plants for sure, they will also make your tank look pinkish. I tried myself different combinations with this tube and other ones (6500 and 10.000 K) just to see if I liked them. I finally didn't use it as the living room looked a bit weird with that pinkish glow. But for sure this pink tube won't make your plants grow better, even if the manufacturer say so...
Hope it helps.
Jordi