Fly fishing strike indicators: the kinds, what each is good at and when to skip them

A nymph does its work where you cannot see it. The line between you and the fly is usually slack and bowed by the current, so a fish can take the fly and spit it out with no tug at all. A strike indicator is a bright, floating marker on the leader that turns that hidden moment into something you can watch: the marker hesitates, twitches, slides sideways or goes under. It also doubles as a depth gauge and a drift check. This guide is about fly fishing only; the bobbers used with spinning gear are covered elsewhere.

TexCast's own indicators: a plug-together foam disc in two halves (a ribbed peg on one, a socket on the other, with the leader trapped between them), a foam ball, and a torpedo float with a soft tube at each end.

Is it just a bobber? Close. Both float on the surface and tell you something is mouthing what hangs below. Fly indicators tend to be lighter and smaller, made of other materials, and used on a thin leader, but the job is the same. Anglers argue about the name and about whether to use them at all; the useful question is which one fits the water in front of you.

What it does for you

• Shows the bite: any stop, twitch, sideways pull or dip is a reason to lift the rod.
• Holds the depth: the distance from marker to fly sets how deep the rig fishes. Slide the marker up to go deeper, down to go shallower.
• Checks the drift: a marker that races ahead of the water around it, or leaves a wake, shows that the line is dragging the flies off their natural path. Mend and try again.

Match the marker to the job

• Heavy flies, shot or a two-fly rig in deep, fast water: a buoyant hard float, or several stick-on dots stacked together. Hard floats hold the most weight and are the quickest to move up and down.
• Shallow nymphing, where the marker sits near the thin tippet: yarn, a stick-on dot or a small piece of putty. They are light enough to cast without tangling and land softly.
• Spooky fish in slow, clear water: the smallest soft-landing marker you can still see, or no marker (see below).
• A lot of depth changes in one outing: anything with a plug, peg, band or screw top that slides along the leader without tying a knot.

The kinds, with what to expect from each

• Hard plug-in floats (cork, balsa or hard foam, round or oval, with a hole through the middle): thread the leader through and lock it with a small peg. Very buoyant, easy to see, reusable and easy to slide. They hit the water harder, which can put wary fish down, and their weight makes them awkward on a thin tippet.
• Twist-on and rubber-band floats (an oval with a slit): the leader slips into the slit and a turn of the float winds the band around it. Same strengths as the plug-ins, and you can fit or remove one with the fly already tied on. They can kink the leader and sometimes slip off during casting.
• Air floats (small hollow plastic balls): float high, take heavy flies and last for years. Some attach by looping the leader through a hole around the ball; others clamp the leader in a slot under a screw-on cap. Like the other hard floats, they land with a plop and tangle more when set on a fine tippet.
• Stick-on foam (small dots that peel and press onto the leader): barely disturb the surface and cast well even on the tippet. They are single-use and lose their grip when moved, so expect to replace one after a few moves, and stack more dots to hold more weight.
• Yarn (buoyant yarn, often pre-treated, tied on with a slip or loop knot, or clamped): very sensitive, soft on landing and fine for the tippet end. It is fiddly to remove, can leave a kink in the leader, soaks up water without floatant and catches the wind in larger sizes.
• Wool and tube (wool stuffed into a short plastic tube): the size and color are yours to trim. Small ones suit spring creeks, larger ones carry a pair of weighted nymphs in bigger water.
• Putty (a soft strike putty rolled around the leader): add a little or a lot, pinch some off for spooky fish, reuse it. It tends to slide off in warm weather, can leave a colored smear on the leader, and picks up dirt until it is a grubby color.

Size, color and where on the leader

Pick the smallest marker that floats your rig and that you can follow. In clear, slow water, one Pennsylvania spring-creek guide keeps indicators to about half an inch long or round, or smaller; a rough riffle hides small markers, so go bigger there. Use a bright color against the water, and change it when glare, shade or foam hides the one you have. Fix a marker on the thicker butt section of the leader when you can, and use a soft marker (yarn, stick-on dots, putty) if it has to sit at the thin tippet end, because a hard float there casts badly.

Setting the depth

As a starting point, put the marker about as far above the lowest fly as the water is deep, then adjust: lengthen the gap if the flies never touch anything, shorten it if you keep snagging. The flies should drift near the bottom, where the current is slower, so a marker that travels a little slower than the bubbles around it usually means the rig is down where it should be. Shot or a weighted fly gets the flies there; see fly fishing weights.

Casting and reading the drift

• Slow the cast down and open the loop. A marker, shot and two flies tangle easily in a tight, fast loop.
• After the cast, mend so the line does not pull the marker. A marker with an upright tip or flag makes drag easy to spot: when it leans or swings away from vertical, the drift is off.
• Set the hook on any change in the marker, even a hesitation.
• Watch for small eddies and seams that bend the drift. Cast again until the marker moves cleanly through that spot.
• Three small markers about a foot apart can also help you keep track of the line while holding it high off the water.

The dry fly as an indicator

A floating dry fly with a nymph on a length of tippet beneath it does the indicator's job and can be eaten itself. It is a go-to rig for many anglers, with two limits. Most dry flies are less buoyant than a purpose-made marker, so a heavy nymph pulls them under, and then neither fly is fishing well. It works best when the nymph does not need to be very deep: pocket water, shallow riffles, or flat water during a hatch with a lightly weighted nymph or emerger. Large foam-bodied flies tied for this job float a nymph well without looking like a bobber.

When to leave it off

On long glassy flats a marker that lands on the water often spooks the fish. Fish a bare leader and watch the line and the leader for a pause, or use a dry-and-dropper. Tight-line nymphing, with the line held off the water and a sighter in the leader instead, is another way to go; if you add a small marker there, keep it from splashing down. Many guides carry two or three kinds and switch with the water, because no single indicator is best everywhere.

Sizes, gaps and drift speeds here are places to start. Water depth and current vary from one run to the next and from one day to the next, so adjust as you fish.

Related guides

• Fly fishing the Guadalupe below Canyon Dam: what the lure rule means for flies
• Fly fishing in Texas: where to start
• Fly fishing weights: split shot, putty, beads, eyes and sinking lines
• Flies from our box: egg, nymph, popper, hopper, streamer and worm
• Fly fishing basics: how a fly outfit goes together

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