Monofilament Fishing Line: What It Is Good For, and Where It Loses

Monofilament fishing line is a single strand of nylon that stretches 25–30 percent, floats or sinks only slowly, ties every knot easily and costs one to three cents a yard. The stretch is the property that matters most. It cushions a treble hook against a thrashing fish, lets a catfish take a circle-hook bait without feeling the rod, and absorbs a trolled striper’s surge. It is also why mono feels dull on a jig, and why braid and fluorocarbon took its place for bottom fishing.

Every property that makes mono worse for a jig makes it better for a crankbait, a topwater or a catfish bait. It is not the old line. It is the line for stretch.

What does 25 percent of stretch do at the rod?

It puts a spring between the rod and the hook. Nylon stretches 25 to 30 percent of its length before it breaks, fluorocarbon 10 to 15, braid almost nothing. With 60 ft (18 m) of mono out, that is up to 15 ft (4.6 m) of give at the limit. At the loads of a hookset it is inches of give, where braid gives none.

That spring keeps a crankbait’s thin trebles from tearing a hole in a jumping bass. It takes the shock out of a striper hitting a trolled plug. And it protects the knot, which is where line fails. On TackleTour’s bench, 10 lb Berkley Big Game broke at 11.8 lb on a straight pull, but at 94 percent of its rating through a knot.

The spring costs hooksets, and the fix is the rod. Jason Sealock’s rule at Wired2Fish is to pair stretchy line with a faster action and more backbone, so the rod makes up what the line softens. Braid, by the same rule, goes on a moderate rod that bends deep; the rods hub explains action and power. A mono crankbait rod can be moderate, because the trebles want give. A mono topwater or spinnerbait rod should be fast.

Where is mono the right line?

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Which test for which fishing?

Each kind of fishing wants its own pound test, and its own kind of mono: limp for spinning reels and light lures, tough for baitcasters, catfish and the surf.

Mono, fluorocarbon or braid?

Mono wins on stretch, price and knots; fluorocarbon and braid each beat it at something else. Mono has been on reels since DuPont sold the first spools in 1939, and the limper Stren of 1959 put it on nearly every reel.

Mono is not fatter than fluorocarbon at the same strength, but braid is a little over half its diameter. On the chart Tackle Village reprints from Oklahoma’s wildlife department, 10 lb mono and fluorocarbon are both 0.011 in, and 10 lb braid is 0.008. At 30 lb mono is 0.020 in against braid’s 0.012.

Against fluorocarbon, mono wins when the line has to float, or when the knot has to be tied fast with cold hands. It wins when cold water turns fluorocarbon into wire on a spinning reel. And it wins when the spool costs more than the fish is worth: a 300 yd filler of mono is a third the price. Fluorocarbon wins where the fish can see the line, where it rubs rock and shell, where the lure has to sink and where the bite has to be felt. The fluorocarbon vs monofilament page settles the two technique by technique.

Against braid, mono wins on stretch, price and knots, and it grips the spool; that is why 20 yd of mono goes under every braid fill. Braid wins on diameter, which means distance, depth and more line on the reel. It also wins on sensitivity, on strength in cover, and on life, because polyethylene neither absorbs water nor weakens in the sun. You can have both: braid on the reel and a mono or fluorocarbon leader at the lure, as on the braided fishing line page.

Where does mono lose?

• Jigs, Texas rigs, drop shots and anything fished on the bottom. The stretch hides the bite and the bottom; fluorocarbon or braid.
• Heavy cover. A 20 lb mono is 0.018 in thick; a 50 lb braid is 0.014. Frogs, punching and flipping want braid’s strength in a thin line.
• Casting distance with light lures. Braid’s thinness and lack of memory cast farther; mono’s coils cost yards.
• Clear water and pressured fish. Mono’s refractive index of 1.62 is farther from water’s 1.33 than fluorocarbon’s 1.42, and fish see it.
• Longevity. Mono weakens in sun and water; a spool that has sat a season is a spool that breaks on the hookset. Change it every three to six months of use, and after any big fish.
• Deep water. Through 80 ft or more of water, The Tackle Room says, mono’s stretch makes the bite nearly impossible to feel; braid.

How thick is each pound test?

The diameter in the small print on the spool decides how far the line casts, how deep a crankbait runs and how much fits on the reel. Berkley’s published figures for Trilene XL (the limp casting line) and Big Game (the tough one) sit beside the chart Tackle Village reprints from Oklahoma’s wildlife department (Trilene and Big Game for mono, SpiderWire Stealth for braid).

The labels are honest. TackleTour’s micrometer put 10 lb Trilene XL at 0.293 mm against a published 0.280, and 10 lb Big Game at 0.298 against 0.300. But the same pound test is not the same line. Big Game 10 lb is 0.300 mm where XL 10 lb is 0.280, because the tough monos buy their abrasion resistance with a fatter strand. On a spool from Europe or Japan, sold by diameter rather than by test, the millimeter column is the one to read.

Copolymer or a bright line?

Copolymer lines blend two nylons, or nylon with another polymer. They stretch less, run thinner for the strength and resist abrasion better, at a small premium. Several of the premium monofilaments on the shelf are copolymers, and Sufix says its Advance stretches half as much as a regular mono. They are the sensible upgrade for crankbaits and jerkbaits, where you want some stretch but not all of it.

High-visibility mono in yellow or orange is the other variation. Fish care less about line color than anglers fear, and a bright main line lets you see the line move before the rod does. Yellow 4 and 6 lb line suits crappie fishing, because most crappie bites are seen rather than felt. Night anglers run fluorescent blue, which glows under a black light. Pair any bright line with a clear or fluorocarbon leader in clear water, and the fish sees nothing while you see everything.

How do you beat the coils?

Memory is nylon’s habit of keeping the coils of the spool. A fresh spool of mono jumps off a spinning reel in loops, and a stiff old one casts half as far. Heat makes it worse, which is why a rod left in a truck cab through July comes out with line like a Slinky. Five things beat it:

1. Spool under tension, wet, to 1/8 in (3 mm) below the lip when you put fishing line on a reel.
2. Soak it before the first cast. Nylon goes limper wet; a few minutes with the spool in the lake relaxes the coils.
3. Stretch the first 30 ft (9 m) by hand. Hook the lure to a fence post, walk back and pull.
4. Pick a limp line for spinning reels. Trilene XL, Maxima Ultragreen and Sunline Super Natural are the limp casting monos; Big Game and the other tough lines coil more and belong on a baitcaster or a catfish reel.
5. Keep it out of the heat, and replace a spool that still coils after a soak and a stretch.

Which knots hold in mono?

Nylon is the easy line to knot. It is slightly rough and stiff enough that five wraps grip, so a knot that slips in braid holds in mono. A rushed knot also costs less than in fluorocarbon, which glazes when pulled tight dry. The rule is still the same: wet it, tighten slowly, trim short, retie after a fish.

The Palomar knot doubles the line through the eye, which makes it a strong, simple hook knot in mono. On nylon, a plain clinch beat the uni knot head to head in Salt Strong’s 2021 pull test on 20 lb Ande mono. Mono to mono within .002 in of each other, 10 lb to 12 lb Trilene XL for example, is the blood knot; for a bigger jump, a double uni. Braid to a mono leader is the FG or the double uni. And the line goes onto the spool with an arbor knot.

Should you use a leader with mono?

Usually not. A mono main line mostly goes straight to the lure: Bobby Lane ties 10–20 lb mono to floating topwaters and crankbaits with no leader mentioned. Add one for a job the main line cannot do. In the surf, a heavier mono shock leader takes the cast, at Sea Angler’s 10 lb per ounce of lead. On a catfish rig, a 40–60 lb mono leader goes below the swivel. Behind a bright line in clear water, a clear or fluorocarbon leader hides the end the fish sees.

When should you respool?

Nylon degrades whether it is fished or not. Sunlight breaks down the polymers that give it strength and flexibility. Water soaks in and loosens knots, salt dries into crystals that work like sandpaper, and every rock, dock post and hookset leaves a nick.

How often depends on how hard you fish. MeatEater’s Alice Jones Webb puts a hard-fished spool of mono at once per season, sooner if it lives in the sun. Angling Sports’ schedule runs three or four times a year for a heavy user, two or three for a moderate one, and once a year for a weekend angler. By the same schedule, a bulk spool unused for two or three years goes in the bin. Braid on the same reel lasts years, which is the second argument for braid with a mono leader: the main line stays and the cheap part gets replaced.

• Read the line, not the calendar. Run it through your fingers from the lure back: rough spots, fraying, a chalky or faded color, stiffness, coils that will not stretch out. Frayed near the lure, cut back about 10 ft (3 m), as Angling Sports advises, and retie; frayed along the whole spool, respool.
• Test it. Tie the end to something solid, walk out 25 ft (7.6 m) and pull. Line that breaks below its rating has gone bad, Angling Sports says.
• Store it cool, dark and dry. A sealed bulk spool in a closet keeps; a filler spool on the dash or in a boat locker does not. Never put a reel away wet. Buy 300 yd at a time unless several reels run the same test; a 3,000 yd bulk spool is old before it is used.

What should you buy?

1. A name-brand filler spool, not a 3,000 yd bulk spool. Wired2Fish’s Jason Sealock names Maxima Ultragreen, Trilene XL and Berkley Big Game (“a pretty good spool for about $10”) among his monofilaments. FishUSA lists Trilene XL from $5.99.
2. Color. Clear or low-vis green for most fishing; high-vis yellow for watching the line on a float rig, or for a bass angler on a leader who wants to see the bite.

The fluorocarbon fishing line page makes the other case, the line hub holds the three-way comparison, and the best fishing line for bass turns all three into a setup per technique.

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