never heard those names, but if you are talking about some similar looking fish its probably the smaller one; Hypophthalmus.
Thats the most common one and goes by numerous names.
You can tell the difference by these pictures, both species young:
Ah. The emperor/imperial ID shark would be the paroon shark then...
All over toronto they sell it as that, and sold for 3x the price of an ID shark, but I couldn't find any info about it. Not sure why they call the paroon shark an emperor ID :l.
probably because of the high fin, so emperor like hehe
they are sold as Pangasius long fin where im from... and go for 5-6x the price of the ID´s
Which isnt that bad, if they were cheap, all the kids would buy them and put them in tiny tanks
I have some very small paroons in my 245 gal tank.
I did not realize they are really aggressive and like eat their tank mates when they got bigger.
They are very beautiful I plan to keep them till they get to the aggressive stage.
The aquarium store that I go to is great, they have some really unusual fish and other stuff. The owner told me that he will take back the paroons when they got bigger.