Full-spectrum light is light that covers the electromagnetic spectrum from infrared through near-ultrviolet, or all wavelengths that are useful to plant or animal life; in particular, sunlight is considered full spectrum, even though the solar spectral distribution reaching Earth varies with time of day, latitude, and atmospheric conditions.
"Full-spectrum" is not a technical term when applied to an electric light bulb but rather a marketing term implying that the product emulates natural light.
Products marketed as "full-spectrum" may produce light throughout the entire spectrum, but actually do not produce an even spectral distribution, and may not even differ substantially from lights not marketed as "full-spectrum"
Lightbox therapy, otherwise known as phototherapy, is a recognized modality for depression (such as SAD). Depending on the quality of the light, it is estimated that 10,000 lux is needed for effective treatment. Not all light boxes are the same
In terms of what colour or wavelength works best for photosynthesis, Red works best, blue light is absorbed but it has too much energy so some of the energy from the excitation is lost through the carotenoids which act to protect the manganese cluster (site of water oxidation). Green light is not absorbed as chlorophyll is not excited by green light.
Bottom line is axolotls don't really like light but live plants do.
Whatever you chose the issue is how much heat is produced and do you have places for your axolotls to go to get away from it