pearls are rather shy unless they are in a group of 3 or more.
they tend to get 4-4 1/2 inches as stated a few time above.
they are very peaceful, one of the most peaceful of the gourami's
also its good to have a ratio of 1 male to 2 females also, unless your actually breeding.....
I have 1 male and 2 female Pearl in my 75G and they love to play in the tank, like all gourami's they can be pushy at feeding time, but other than that they are a great community fish.
and the best looking gourami in my opinion