Hey,
Rather than go into a whole disertation on the subject as there is so much already written on the subject of size here and disposition; suffice it to say that, adult blood females are larger than their male counter parts and can get to be as large as 6-7 feet and weigh as much 40-45 lbs. Males get to be 5-5.5 feet and weigh as much as 30-35 Lbs. These are rough lengths and weights and can vary from animal to animal and feeding schedule and type of food item.
Their disposition can also vary accordingly too, depending on whether the animal is wild caught or cbb. With any luck and some smart buying and proper research on your part, you'll only buy from a reputable breeder or dealer and get only the best animal possible. With wild caught bloods you are adopting a whole host of problems and bagage that as a first time blood keeper you don't want to deal with right off the back. Start with a cbb blood and one that is well adjusted and feeding with all the proper cage and history records to prove it available to you.
Check out Kara, from Nerd or ProExotic for the best available bloods. And of course there is also, VPI.
-Angel
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"Until we lose our self, there is no way of finding our self."
-Henry Miller.