Original sentence: The Halibut is blackish-grey on the top side and off-white on the underbelly side.The Halibut is the largest of all flat fish, with an average weight of about 11 - 13.5 kg (25 - 30 lb), but they can grow to be as much as 211 kg (465 lbs)
Edited sentence: The Halibut is the largest of all flat fish, with an average weight of about 11 - 13.5 kg (25 - 30 lb), but Halibuts as large as 333 kg (734 lb) have been reported as caught; the largest recently recorded was 211 kg (465 lbs) and 2.5 m (8 ft)  long.. The Halibut is blackish-grey on the top side and off-white on the underbelly side