I have 4 Gourami's in my tank. 2 kissers and 1 Opaline(the bully) and 1 blue. The LFS told me that they'd be fine in my tank, but in doing some research to decide what else to put in my tank, I've come across taht they will get pretty big. If so, how long does it take to reach the 6-8 inches that I've seen they should be. I have a 30g. tank.