a big one lol it says a 300 for one and if you want 2 of them i would say at least a 500 or 600 and thats probably to small for an full grown adult so you would have to upgrade, i believe they get around 4 ft. i could be wrong.
in sharks and rays it says most horn sharks do not exceed 37.8 " and can weigh over 22lbs. They like colder water 55 to 70 degrees and i was wrong in the book it says they need a 240 gallon but people say that this book runs small on tank sizes so......
No species of Horn Shark gets 14'.
The California Horn (Heterodontus fransisci) is the biggest, maxing out at 120cm (46.8").
For 2, I'd suggest nothing smaller than a 500gal. tank, in an irregular design (square or something like that).