Is it safe to take fish oil in big amounts?

Taking anything, including food items and supplements, to excess is not good for you, if not actually harmfull. You should always seek professional advise when it comes to health -- you only have one body, and you only have it for a short time, so look after it.

On the subject of fish oil, Omega-3 fatty acids, present in oily fish, have been shown in trials to lower the risk of sudden heart attacks. Eating oily fish as part of a varied diet is much the best option, but fish oil supplements, IN MODERATION, can be beneficial.