I bought 2 arows, the first was 4" and was in the tank for 2 months before i bought another that was 5" ( the 4"er was about 6-7" at the time the new one was put it) there was a couple fights at first but I seperated them. when I woke up in the morning he jumped to the other side with the arowana and were swimming around fine. they fought every now and then but They are both in my 360 now and are a good 16" or so.
please post pictures soon..