Grizzly salmon oil, Kronch, Fish 4 Dogs, Angell petco are all good. I'm using Riaflex Salmon oil at the mo as my raw supplier sells it, been through several bottles now and I like it. Also be sure to supplement with vit e if giving fish oils :)
You can buy vitamin e from health food shops, make sure it's natural not synthetic, my 17kg and 23kg dogs get 200iu two or three times a week, 32kg dog gets 400iu. I get mine from Holland and Barrett :) fish oils deplete the body of vit e.
Would never use Krill oil as it is from the food(ie Krill)that sustains some species of Whales & other marine animals. It's being touted as sustainable by the likes of that woman who was on Countdown as the maths genius. It isn't truly sustainable as it cannot be "produced"by farming like salmon etc