Lindsay is ten inches tall from the top of his fin to the bottom. He is a black marble but he also has some orange on the top of his head, which is a very desirable feature in black marbles.
He is less than two years old.
Angelfish can live to be 10 years old if kept in the right water conditions. They mate for life. The easiest way to get at least one pair of angels is to buy several at a time and put them all in the same tank. You'll soon see them selecting their mates. When they do, they will almost never leave their mate's side.
Last year, I bought 11 angels - 5 koi angels and 6 blues. Out of that batch, I have 2 koi angels who have paired off, two blues that have paired off, and two blue marbles that are uneasily paired off - I don't know if they are male buds or a bickering married couple.