On tackletour one of the guys tied a fluoro leader onto braid using the Alberto but he mentioned that he tied up the tag end of the braid. Does anyone know what knot he used?

I personally think it's unnecessary.

Having used the alberto on nearly every rig I own for the last 4 years, i can unequivocally say that if tied right, a stopper knot is completely unnecessary.

No stopper needed.

I've only tied one Alberto knot.  Braid to 12 lb. mono leader.  First time out I got caught on the bottom.  Had to wrap the line around a piece of limb to pull it loose.  Everything held.  Doubt you need a stopper knot.

As everybody else said, it's unnecessary.  I've never broken an Alberto knot when it's been properly tied.

Good deal. Thanks guys. I usually seal it up with a little super glue anyway.

While we are discussing it....can I cut the tag ends as short as possible as long as I don't touch any part of the knot itself?

If you tie it down right, and cinch it down you can trim the ends as close as you possibly can. Doing this will also help the knot slide through guides easier.  The super glue isn't needed with this knot.  If you wrap it properly ( think XXXXXX) it will seat perfectly.  People use super glue on knots like the uni-uni, not for knot strength, but to help smooth out the knot.