My experience is that the larger ones will always beat up on the smallest ones, which will then stop eating and will waste away unless you move them out.
Once you do this, then the big gatf's will pick on the next smallest ones, and so on...
Having only two large ones will mean a quick death to the weaker one...believe me, I know by experience.
Look at what a 15" gatf will do to a feeder goldfish...it will try to do the same to another gatf.
Maybe if you had a really huge tank, the fish would be able to escape attack and avoid much of the stress that will cause them to waste away, but hardly anyone has a tank this size already or will ever get one, no matter what they say right now.
So it's probably best to keep just one.
Believe me, I've tried to do what you want to, and it just does not work and is not practical...you're better off blowing your discretionary $$ on other things and avoid all the stress.
BTW, 3-4 yrs. ago when these fish were really uncommon and $600 or more, I had more than a dozen in my tank (I didn't pay that much though) and it was cool for a while.
I remember that some of the first ones I saw for sale were over $1,000.
They were kept with a dozen vatf of the same size, but after a few months the vatf's were sold off because they were beating up the gatf's too much.
Once the gatf got a little bigger, they started to get a lot more aggressive and the smaller ones started getting beat up really bad.
Every day when I got up in the morning, I expected to see dead or shredded tiger fish in my living room tank...that was a ****ty feeling!
I sold some off, some wasted away and bit the dust, and for the last 2 yrs. I've kept the last one in a community tank with other big fish. It's about 15" right now and doing well.
BTW, the one I kept was the largest and most aggressive one of the school and it terrorized all the others before they were sold off or died. It's the big one in the middle of the first picture.
Ironically, it's the one fish in the tank which gets it's ass kicked every once in a while. But they are quick healers and it always recovers after a week or two.
Hope this helps.
