Indicator Nymphing for Trout: A Beginner Setup

How to rig a strike indicator for trout: where the float goes, how far above the fly to set it, what a take looks like, and one test before you change flies.

From the book Fly Fishing for Nerds — $9.74 →

When no fish are rising, a take happens under the surface, where you cannot see the fly. An indicator is a small float — yarn or foam — that pauses, twitches, or dips when something takes the nymph. This page is that rig, the depth setting, and a short test.

Pick the lane before you pick the fly. A read of the reach and a look at cover, depth, and current give you one target. The indicator only reports what happened in the lane you chose.

1. Use it where you can watch a float

An indicator earns its place in water deep enough that a dry fly is in the wrong layer, and slow enough that the float can travel with the bubbles. Knee-deep to waist-deep runs, the head of a pool, and the slow side of a seam are the usual places.

Fast, shallow pocket water fights this rig. The float catches current, the fly swings up, and the drift becomes a series of mends. Those pockets want less line on the water. Fish them with the pocket-water checklist, in close. Save the indicator for water where the float can actually drift.

Tight-line nymphing — rod high, no float, watching the leader for a twitch — is a different method for that close water. Learn it after you can already get a dead drift and recognize a take. Until then, watch the float.

2. Rig it once

Start from the floating line and the 9-foot 4X or 5X leader in a first outfit. The same pieces are on the gear page. Tie a fresh piece of 4X or 5X tippet to the leader, so you are not chewing up the tapered end every time you change flies, and tie one nymph to the tippet. A Pheasant Tail is enough for the first session. Which of those X sizes to use, and how long to cut the piece, is the tippet size guide.

Put the indicator on the leader, above the tippet knot, where the leader is still thick enough to hold it. It has to float, and you have to see it at casting distance without hunting for it. Yarn and a small foam float both meet that test. Lock it so the cast does not slide it down onto the fly. A float that creeps has changed your depth before the drift starts.

Start without split shot. A bead on the hook is already weight. Add one small shot a few inches above the fly only after a few drifts show the nymph is not getting down. Shot on the hook, or shot that slides down onto it, snags and kills the action.

Nippers belong in your hand for this. A clean tag and a knot you would trust on a fish are part of the rig.

3. Set the depth, then let the river correct it

Current lifts a nymph, so the distance from indicator to fly needs to be longer than the water is deep. A workable first guess is about one and a half times your depth estimate. In water around knee deep, start with the float roughly two to three feet above the fly. In a waist-deep run, start near five feet. The next drifts revise the guess.

To fish deeper, lengthen the distance from float to fly. To fish shallower, shorten it. Move the indicator, or change the tippet length. Rebuilding the whole leader for a one-foot change wastes the hour.

Read the bottom. A tick of gravel on every pass means too long or too heavy. Shorten until most drifts travel clean and an occasional tick says the fly is near the stones. A fly that never ticks, in a slot you believe is deep, is a reason to lengthen. Judge that against the bottom you can see. Polarized glasses, the same ones on the gear page, make both the float and the bottom easier to see.

Cast upstream of the spot you mean to test, so the nymph has time to sink before it arrives. A fly that reaches the lane still on the surface never ran the depth test.

4. Count only the drifts that match the bubbles

The indicator should move at the same speed as the foam and bubbles beside it. If it races, stalls, or cuts across the lane, the nymph is dragging. Mend upstream as soon as the line lands, and keep extra line off the water. In faster current, a higher rod tip helps. A short drift that tracks the bubbles is the test. A long drift that skates does not count.

The tippet below the indicator should sink. If it lies on the surface, rub it with a bit of silt from the bank. A floating tippet holds the fly up, so the depth you set never happens.

Stand so the line and your shadow do not land on the lane first. If the only way to reach the slot is a wade that looks wrong, pick another lane.

5. Set on the odd movement

A take is often a small event. The float pauses while the bubbles keep going. It twitches, slips sideways, or dips and stays down. Sometimes it is simply no longer where your eye expected it. Lift the rod when the float does something the current did not. A trout can take a nymph and let it go before the indicator plunges.

A short lift is enough. A hard sweep on 5X tippet breaks the fish off, or pulls the fly out of a lane you were still fishing. If every supposed take is a rock, you are too deep or too heavy. Shorten, and run the same lane again. Rocks repeat. Fish do not.

6. Change one thing, and write it down

Give one lane a handful of clean drifts with one fly at one depth.

• If the drifts dragged, fix the drift and repeat the same rig.
• If they were clean and empty, change the depth.
• If the new depth is clean and empty, change the fly, or move to the next lane.

Depth and fly are separate questions. Changing both at once leaves you unable to say which one mattered. When the fly is the thing you change, use what to tie on when nothing is hatching.

A dry fly with a short nymph under it is a different rig, for when you think the fish are close to the surface. The dry is the indicator. Keep the dropper to about a foot, or a foot and a half in slower water, or the dry will skate and you will have tested neither fly. Run that as its own trial. The dry-dropper guide is how to tie it and cast it. The dry-or-nymph guide is how to decide you are in that layer before you build the rig.

One line in your phone before the next bend: lane, distance from indicator to fly, pattern, result. After a few runs you can see whether you fish every lane at the same depth.

A creek that was stocked this week is the same rig, pointed at a different spot. The stocked-trout guide is where those fish sit the first days, and which fly to try next.

The longer treatment of rigging, drag, and this loop is in Fly Fishing for Nerds: A Data-Driven Guide to Finding, Hooking, and Landing Trout. Readers can take 25% off ($9.74) with code NERDS25 at https://leanpub.com/flyfishingfornerdsadata-drivenguidetofindingfishfly-fishing-for-nerds/c/NERDS25.

The Riverbank Checklist is the one-page routine to run on the bank before you tie the rig.