My dats are great when the lights go out.....

[Ade]

I have 4 NTT's and 4 ITs. I agree with the subdued lighting option. You might try starting dark and then slowly brighten it up over time, until they are use to it. I'll probably try that out soon and see if I can get my dats accused to the brighter lights as well.

When my aquarium lights are on, all my dats hide or turn dark in color just like yours. However, once its off, then they are out and about and at the front of the glass begging for food... so its totally the same here.

I use subdued lighting: on a timer for about 15 hrs per day. I ONLY feed when lights are on. Most of my tigers are stable and display alo tof the time.
It helps of there are other tigers, 5 or more, and lots of dither fish.
BUT tigers can take ages to settle in.sometimes years