I learned many years ago to not use a strike indicator on the smokies streams by one of the best nymph fishermen around. Jim Parks taught me to high stick instead of lobbing a bobber & nymph rig. Its much more effective. You want a tippet connection knot about 2-3 ft above your top nymph. You watch the knot as you high stick the run. Another method is to intentionaly put a soft kink in the leader at the same location. When a fish bites, the kink with straighten out and you set the hook. Both methods are very effective and no bright yarn or bobber to spook wary fish.
For very low light conditions I will add a tiny piece of the foam roll-on strike indicator (made by Cortland in flat sheets) on the knot.