Yup, not all agrees on ways to bring out the best in our pets. Anyway, another thing I didn't share is because I'm not sure if it works on red arowanas too, but it's an interesting thought. I don't use normal arowana tanning lights (whether they are marketed for red, gold, 24k etc). I wanted to get a true full spectrum lights. Did some research and found Samsung chips are best. When I finally bought one, I found out ironically, the light I bought are full spectrum except UV (meant for hydroponics).
Before I continue, I will add that I still insist that genetics play the biggest part in the development of your arowana.
I do have one golden arowana that's kept indoors without direct sunlight at all. It is also using the same lights I'm using with the initial experiment with full spectrum lights as I didn't know it doesn't produce UV spectrum yet. I found that the full spectrum does make the gold rims on the edge of the golden arowana scales more intense.
Red arowana will have the parts where the gold is to be red. I haven't tried out on a red yet. I will think a full spectrum meant for nature style aquascape lighting will function the same. But at night (this is probably cuz mine doesn't contain UV) my tank will look a mellow yellow/golden colours and it's not easy to see the blue in blue base arowana. That will be your drawback if compared to lighting that produces white light for eg. But otherwise, my arowana seems completely relaxed with that light. I'm not sure how this information will help you, but if you're up for unorthodox methods, here's one. Haha....