Growth rate very fast in the first year till 18"-25"+ and slow down. For tank mates I recommend no tank mates unless you're able to pull off my style. Lol!
I dunno. I purchased a 4-5 inch Dolloi about 2 years ago and I haven't seen a whole ton of growth on his part. He's maybe 10 inches now. I kept him with clown loaches for a year or so but have since moved him to his own tank. I never noticed any aggression but he seems to have a better appetite in a smaller tank with no company.