Nice topic! Two quick items:
(1) The previously posted color-temperature-plant-pigment graph is very, very useful! Everyone should keep a copy of this. https://www.aquaticplantcentral.com/f...f?d=1149132070
(2) The Kelvins number for flurescent tubes, by itself, is almost too much of an approximation to be useful. The number is supposed to represent radiation discharge from a heated object. If this was the case, it would have some sort bell shaped curve where the peak occured at the associated light wavelength for that temperature. Due to the laws of physics of how fluorescent tubes work, phosphor atoms lining the glass tube release photons at very specific frequencies, which do not at all generate a smooth curve one should expect with a Kelvins number. Different phosphors have different spectral emission patterns. Application
Each manufacturer/model tube is different. It's Kelvins number just means that there is a strong emission line at that frequency. Get the emission chart for that tube. Compare your tube's chart against the color-temperature-plant-pigment graph. Tube emission peaks not in the plant graph are ignored by your plants. The more the tube phosphors emission peaks conform to the plant graph, the more useful the tube is to your plant. Examples
Q: So are true actinic bulbs beneficial for planted tanks or not?
A: Let's look at the chart. 420 is where the peak starts to rise for several values. This means that there will be some useful light, but it won't be optimal. (Kinda makes sense since Actinic is optimized for marine corals and not plants in general.) Another tube selection will provide much more benefit. With the cost of actinic tubes, it's probably a waste of money for a plant tank unless you want to show off some of those new glowlight anios.
Q: 420nm is near but not inside any of those ranges you (Nate's earlier post) gave for essential plant functions.
A: Let's do a sanity check on those numbers and what they mean against the chart:
For green plants the lighting peaks that are most important: |
The above numbers do identify the peaks. Therefore, same conclusion as before.
Q: What about 10,000K?
A: Each model of a 10,000K tube has a different emission spectrum. Obtain the spectrum chart for the particular manufactured bulb and see how the peaks line up to get your answer.