I think they will be fine in the tank for at least another year. as i said the Tigers do grow slow, my plan from the beginning was to grow one large specimen vittatus as this is still my favourite of the tigerfish species, so basically i bought 4 to start with then added to that as they became available to me and i was also very lucky to accquire two Goliaths which i in turn grew up and sold one on, so basically i would probably start selling them off as they grow and keep the one i like the look of the most, as you know each fish varies in appearence and tooth size etc. I believe with the right size tank there would be no problem keeping a school of these at a larger size, even though they do fight from time to time the intent is not to kill or seriously injure each other its more like play time for them as they chase each other, and as long as they are well fed i cant see any problems, mine have plently of space at the moment in the 6 foot tank. Good luck if you decide to set up a tiger tank i would definately recomend keeping tigers of all the pedatory species and believe me ive kept most, none compare to Hydroynus.