There are two main differences between krill oil and fish oil supplements. One is, the omega-3 fatty acids in fish oil available as triglycerides and those in krill oil are in the form of phospholipids. Studies suggest that krill oil has a higher bioavailability than fish oil (7). The second difference is krill oil is rich in the antioxidant, astaxanthin, which also provides the oil with a deep red color. Astaxanthin is only found in salmon or trout and is not common to fish oil.