Expect them to get about 8''-10'' how ever 12'' can be reached in home aquarium. They will need at least a 55 gallon but a wider tank would be better for adults.Mine group of 3 grew from about 5''-6'' to 7''-9'' in around 4 months. They like a little salt in there water as we'll. It can be tuff to get them to eat prepared foods such as market shrimp, earth worms, Krill and fish fillets. So expect to buy some minnows or goldfish but keep at it they can be trained to eat other things. I got my old needle fish to eat prepared foods, one would even eat pellets !