Must agree with Fishpower. TIgers establish a pecking order generally on size and sometimes temperament of each individual fish. I went mad an in the last 5 weeks I 've gone from 4 tigers to 9 now. I have 8 IT's and 1 cambeli. The Iino Tigers are:
9", 8", 7", 6", 6", 5", 4", 4", 3" thats 9. Even thought the biggee is the boss, he never attacks or harms anyone. In fact he often breaks up the squabbles and chasing of the othewr similar sized tigs, just by his presence of swimming in close proximity of the smaller ones fighting.... A kinda nice harmoneaous balance I think.
For those not lucky enough to keep a pulcher (like me), Indos are the next best thing I think, as a group of Dats. However, though do go in and out of stability, compared to Pulchers. What I tend to do is 2 water changes a week, 25%, blue background, minimal bogwood and decor, good feeding, but not overfeed which is well hard as the thing I love most about tigs is the way they feed!!

, only if u got space try to keep 1 or 4+ nr.
Also, don't mess around with stuff in the tank too much. Decide o something, like bare or Decor tank, and stick with it for at least 3 to 4 weeks.
Hope your little tigs stabalise.