The best brands IMO are Blue Ice from Green Pastures (I give my children the fermented CLO), Dr Rons (made by Green Pastures I believe) and Radiant Life, Premier High Vitamin CLO.
provides the links of where these oils are available and dosing information and this article
explains the manufacturing process and goes into the various brands of CLO. AFAIK, Carlson's falls under category 3:
|Fully cleaned and deodorized cod liver oil with synthetic vitamins added back in. Most of the cod liver oils on the market fall into this category. (You’ll need to check with the individual manufacturer to verify whether their cod liver oil falls in this category.) These vary in dose from about 1100 to 4600 IU vitamin A per teaspoon and 180 to 460 IU vitamin D per teaspoon.
Whereas, the ones listed above, are in category 4:
|Fully cleaned and deodorized, with natural vitamins added back in, standardized at 2340 IU vitamin A per gram (11,700 IU per teaspoon) and 234 IU vitamin D (1170 IU per teaspoon). This is the type of cod liver oil sold as Blue Ice and by Radiant Life and Dr. Ron’s UltraPure.
I give my children the fermented CLO
because it is is higher in vitamin A and D, so they don't need so much at one time.