The Black Shark I May Be Able To Keep

[Fizban]

i kind of like the shark now ......i hate giveing fish away that i like what sort of size tank would i need to get for it to grow to be an adult size and be okay i saw a second hand 100 gallon tank 4 foot long 2 foot high ........the guy may have other tanks like that but if posible that tank was a nice price and the size will fit well in my house ? so what size tank do you think would be good ? thanks for any replys