What is the best way you can tell the s*x of an Albino rainbow shark?

Question

really want to add a "friend" to my male while there still young, hes not albino, and yes the tank is big

Answer 1

Whether or not you get a Shark of the opposite s*x, there WILL be fighting.  Rainbow Sharks are entirely intolerant of their own species or fish similar in appearance.  Unless you get a 75+ gallon tank, I would strongly suggest you consider otherwise, as one or both fish will end up dead or injured.