The first time I attached a short fluorocarbon (FC) leader to the end of the nylon monofilament spooled on my reel was more than 25 years ago. I’ll admit, I was skeptical. The hype I’d read about fluorocarbon seemed to imply that fishing with it could be an almost magical experience.

The advertising indicated that fluorocarbon line was less visible to fish than clear monofilament line. I couldn’t see any difference; could the fish? Did it really make much difference to the fish?

I’m a “seeing is believing” sort of guy, and by the end of that fishing trip, I was well on my way to becoming a believer. I was fishing on a large boat with several anglers on either side of me. We were fishing for the same fish with the same bait. I caught more and bigger fish than the others.

Those around me noticed, and eventually, I handed a length of FC line to the guy fishing next to me, after which he caught as many fish as I did—and we both caught more than the others.

Further tests, matching fishing with clear monofilament line alongside FC line, were not always so convincing; but I’m still using FC line (mostly as leaders) 25 years later, and I’ve developed several undeniable truths about fishing with it:

1. Sometimes, using fluorocarbon makes a great difference.

2. Sometimes, using fluorocarbon makes no difference.

3. There’s never a time when fishing with FC line makes fishing less productive.

If these are undeniable, then there is one more undeniable truth: A person is stupid to fish and not use fluorocarbon line—at least most of the time, especially if catching fish is a high priority when going fishing. For me, catching fish is always a priority.

When I started using FC line, I had some questions, and my decades of experience has given me some answers.

First question: What’s the difference between FC line engineered to be used as leader material, often sold as 25- or 30-yard spools, and FC line sold on 150-yard “reel filler” spools?

Price is one difference. A 25- or 30-yard spool of FC leader material costs almost the same as a 150-yard spool of “reel-filler” fluorocarbon. Both kinds are less visible underwater than traditional monofilament.

The other difference is that FC leader material is stiffer and more abrasion resistant. If you are fishing around cover or close to the bottom where the line will frequently rub on rocks, docks, mussels or other potentially abrasive objects, the leader material is a great choice. The reel-filler spools of FC line are softer, less stiff and will “fish” similarly to conventional mono.

I’m frugal, so I buy reel-filler spools and cut leader-lengths of FC line from it to make leaders to use whether I’m trolling, casting or jigging. I check it often for abrasion and replace the leader when necessary. For me, the cost difference makes up for having to make new leaders when I find rough or rubbed spots.

Another common question is: “How long should a leader be?” I like to answer, “How smart are the fish you plan to catch?”

Obviously, some fish are line-shy at least some of the time. They see the line attached to the bait or the lure and refuse to bite. That’s smart, but how smart are they? I’d bet a 6-inch leader would be long enough to fool some of the line-shy fish. A foot-long leader would fool even more, and a 3-foot-long leader will fool about 99 percent of the high-IQ fish in the places where I fish.

I don’t often use a 3-foot-long leader. Instead, I usually use 10- to 15-foot leaders. Not because it takes that much to fool the fish. It’s “knot” insurance for when I have a spunky walleye, trout or bass on the line. As a fish is being subdued, the final portion of the fight is when the maximum amount of pressure is being applied to the line. The line-to-leader knot is a weak point, and a long leader means that the knot is spooled on the reel by the time the fish is cranked close to the boat, pier or bank.

If you want to be a smart angler, or at least smarter than the fish you are trying to catch, use FC line. Remember undeniable truth number 3: There’s never a time when fishing with fluorocarbon line makes fishing less productive.

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