Goldfish compatibility and tank size

Question
Hey,Recently they gave  me this huge fishtank thats 86 Gal in wich i had 5
comets and a small pleco and a small koi until this saturday when my dad
came back home with 2 orands and 2 small irracident or pangasius sharks
since i had no other tank i had to put them there.The guys at the local pet
store said that fancy goldfish and comets shouldnt be mixed but since the
fishtank was that big that i could have them together and they also said i
could have the pangasius sharks tehre without any problem.
Q1.Can i have fancy and comets in the same tank?
Q2 is my tank overcrowded?
Q3 Are the pangasius sharks compatible too?

Thanks for everything ( sorry for the bad spelling english isnt my primary
language

Answer
Goldfish can be mixed so long as their eye handicaps are the same.  The reason to make sure they have the same eye handicaps is that the fish with perfect vision will eat all of the food while the fish with the eye handicap will starve.  You can have fancy goldfish and comets together but you have to watch that all are eating and that there is no aggression going on... goldfish are famous for plucking out each others eyes... Your tank is not over crowded but i would not add anything else to it either... The catfish... sharks... are going to get rather large... up to two feet or more. Each of the goldfish will reach a size of about 12-18 inches... this is why you CAN NOT add more fish to your tank.  The two should get on well together so long as they are fed.  Water temperature should be 72-79 degrees.   dave