You are right.
Normally when nymph (Or wet fly)fishing I use an indicator, this can either be wool or foam. Some people use a floating putty.
I've found that sometimes trout will strike at your indicator, so why not use a dry fly instead.
This has worked well for me i.e. A big visable dry fly with some flourocarbon tied to the hook shank then a nymph (Wet) trailing 2 feet or more (In deeper water)
In some places fishing laws limit the amount of hooks you can have on your line.
So pays to check that your set-up is legal. Two maximum is O.K. round here.