I have a small 2 inch Kisser, they tend to reach sizes between 6-12 inches. Mine is currently in a 50g but I will move him to a 10g of his own so he can grow out abit before going into the Gourami tank. I have already started to see signs of aggression with mine as he is growing so I have no doubt he will get abit more moody with age. As for size, I said between 6-12 inches which is abit vague, however, I have had ones that reach a max. of about 6" and stop growing and one I had reached 12.5" so it is abit variable. Mine have never eaten smaller fish but I have heard of them doing so, I have also found that the bigger they get the more arrogant and aggressive they become.