Lotech,

An 18 inch piece of fluorocarbon tippet won't cause a dry fly to sink. Maybe if I was fishing with a size 28 to 32 or something but then I won't be fishing that small. Most of the time the fluorocarbon still floats, as indicated in other replies, but if it does sink, there is so little of it that it does not pose a problem. The guides I use prefer flourocarbon because they want to improve a clients chances of catching fish and flourocarbon does do that. I use flourocarbon tippet on dries and while nymphing. I prefer not to put a split shot on fluoro tippet so I place a section of fluoro tippet at the end of the mono leader, placing the split shot on the mono at the knot, then tie on my top nymph onto the fluoro, then another section of fluoro to the dropper nymph. When using a dry dropper, be it another dry or an emerger, fluoro also works great.

Larry ---sagefisher---