straing that, \i found blue background works better, but i \have only had \it, \ntt and \ngt.
also i have quite low temp, around 23 C, and this has helped with stability.
I think u shpould try all the factors: lighting, backgrounds, dither fish, dcor, no-decor, and if none of those work, then its down to the genetics of that tiger, some just arn't ever stable.
to confuse things even more, I 've had unstable tigers for years, and 2 have now turned realy stable and beautiful.
Also, it seems pulchers are the most stable of all the tigers. though NGT's can be equally as srunning IMO. why dont u get one of those Berserker.?