Originally Posted by silver creek
So you can leave slack between the indicator and the fly to get the fly to sink lower and drift at the speed of the deeper water, but the indicator will not indicate the strike.
On the contrary, if the distance the trout has to travel back to its feeding position is greater than the amount of slack between the nymph and indicator, the indicator will register a delayed strike. If you are constantly aware of the position of your nymph, the indicator, and the best spots for feeding trout, you can have slack and still not miss strikes. It takes practice and experience, but I feel that you're selling indicator fishermen short.
And, you can use the indicator for depth control when your nymph is swept from the riffle into the slack water below it. You get the best of both worlds.