Omega 3 is somewhat necessary these days, IMO, because the meat most of us are feeding our dogs comes from poorly controlled pastures and the animals are "finished" way too fast, much faster than would occur normally in nature. That results in a higher omega 6 component and throws the whole 3-6 balance off.
Your dog will not likely suffer too much harm though. You may notice with supplementation that your dog has a shinier coat. On the inside, omega balance helps the heart and brain function more efficiently.
I keep a plastic shoebox in the fridge to defrost the dogs' meat bags. I also use that box to remind me to add certain things like an egg, oil, yogurt for the next day. I'm pretty brain dead in the morning and really busy at dinnertime. So throwing the items in the box when I pull food for the next day really helps.