Like i said i will probally be getting 3 of them. ive heard that 2 dats usally dont work.
I tend to disagree with the idea that two cannot be housed togeather. I've kept two togeather a few years back at about 9" & 4.5" and had little to absolutely no issues. They were housed with around 5 other tigers including IT and NTT and everyone was quite well fed on market shrimp and Massivore.
I won't say aggression can't happen all togeather as NGT as with any fish will vary from individual to individual. I think people may notice aggression between two individuals more often woth NGT than say IT for a few reasons. Primarily, they're a more expensive fish! I'd bet most NGT keepers tend to pay a little more attention to the $100-300 fish. Also, most of us are less likely to fork out the cash for two fish of that cost in one tank, not saying it doesn't happen but I would imagine the pool of examples of two NGT vs IT in a single tank to compare is a lot smaller in the NGT column. I know it exists, however rare, but how many people have you seen who own 3 NGT at once? You're realistically looking at $360-720 right off the bat. I would imagine that if maintained normally in say a 180-210g aquarium 3 or more NGT would coexist similarly to IT of identical size.
In my own experience IT display just as much aggression when 2 individuals are placed in a tank togeather. It's more so the lack of a heierarchy or pecking order that causes "increased" aggression where instead of being dispersed that pecking all goes to one individual.
But you stated possibly getting 3 which is awesome. I think you should be ok but keep us posted and I would especially be interested to hear how it works for you.