one what does the hot spot need to be?
No hot spot for cresties, they do not require any additonal heat.

Ive read that as longs as your house is nice and warm (which i know mine is) they dont need a heat source? Is this correct?
Yes, as long as you keep them in the high 60's and low to high 70's you are good.

Also can they be kept in tubs
Yes but unlike BP you want a tub with a nice height.

You will find more helpful info here.

http://www.ball-pythons.net/modules/...ewarticle&id=6