Initial Posting: 3/2/2017    Last Update: 7/25/2017
Answer: You can get the omega-3 fatty acids EPA and DHA from the same place that fish get theirs — algae. Because algae is lower on the food chain than fish, omega-3's from algal oils are naturally less contaminated than oils from fish (although fish oil in supplements is purified, removing most of these contaminants, as shown by tests by ConsumerLab.com).
Another advantage of algal oil over fish oil is that the EPA and DHA are in the triglyceride form — which may be somewhat better absorbed than the ethyl ester form found in many fish oil supplements In fact, an increasing percentage of fish oils are now sold in the triglyceride form, possibly for this reason.
However, algal oil is typically more expensive that fish oil and, based on tests by ConsumerLab.com, algal oil supplements do not contain the omega-7 fatty acids found naturally in fish oil, which, preliminary research suggests, may help reduce inflammation and improve cholesterol levels. (Be aware that highly concentrated fish oils also tend to have very little omega-7, as it is removed during processing in order to increase the concentrations of EPA and DHA).
The bottom line: You can certainly get EPA and DHA from algal oil -- it will just cost you a bit more than from most fish oils. Other alternatives, such as flaxseed oil, echium oil and chia seeds provide the omega-3 ALA, but do not provide the EPA and DHA found in fish and algal oil.