I use to own 3 black tips a number of years ago. I had put it in my 20 gallon tank where they grew from 3 inches to about 6 inches. Afterwards, I had purchased a 90 gallon tank and they continued to grow to 8-9 inches. Unfortunately they developed ich and died when our weather soared to 33 C and I had no way of keep the water temp down
I was told that depending on the size of the tank, these "sharks" can grow to 12-13". My sharks loved to eat blood worms, although they will take anything and everything else if nothing else is given. However, if you habitually give them blood worms, it will take a while to ween them to another type of food. Black tips are generally very peaceful fish and love to swim against currents from filters, however, don't put any fishes that are smaller for they will eat any fish that will fit in their mouths. I made the mistake of putting my betta in with the sharks and when the sharks grew 7 inches, my betta disappeared and one of my sharks had a big tummy!! Hope this helps!