The first tenkara line was made from twisted horsehair. Most are now made from nylon monofilament or fluorocarbon fishing line. The two main types are tapered lines and level lines. In the US, most tapered lines are really just long furled leaders. Most level lines in both the US and Japan are fluorocarbon.
If there is one area of tenkara fishing where I get away from the simplicity, it is with the lines. You can certainly choose one line, either tapered or level, and do all your fishing with it. I like to fine-tune things a bit and prefer to use different lines with different rods. To some extent, I'll also match the line to the fly, using heavier lines with heavy or wind resistant flies. I also match the line to how much of a breeze there is. In every case, though, I'll use the lightest line I can get away with.
As with everything else in life, the choice of which tenkara line to use is a compromise. Each type has advantages and disadvantages. I believe that anglers in Japan pretty much choose to fish tapered or level lines, and don't switch back and forth. Here in the US, tenkara anglers do not always follow Japanese tenkara tradition.
To me, the greatest single advantage of tenkara over Western fly fishing is the improved presentation. The long rod and relatively short line allow you to keep most of your line off the water and fish a tighter line. To do this effectively, though, you need to fish a very light line.
For years, I recommended fishing the lightest line you could get away
with. A light line is easier to hold off the water's surface, and keeping a hi-vis line off the water at all times is directly related to catching more fish. To some extent, how light line you can fish will depend on your
rod, the flies you are fishing, and whether there is any breeze. Casting into a breeze or casting a wind-resistant fly requires a heavier line.
I have come to mostly agree with John Vetterli's assessment, which is the line to use is the one which best loads the rod. Stiffer rods need heavier lines. As a general rule, for a Nissin 6:4 rod or Daiwa level line rod I might use a size 3 level line, while I might go to a size 3.5 for a Nissin 7:3 rod or a Daiwa LT rod. The LT rods would also do well with furled lines, which are almost always heavier than level lines.
I would also recommend fishing a very visible line, as I am convinced that that the better you see your line, the better you'll see the strikes
If you want to embrace the simplicity of tenkara, this section should help you pick which line to use. If you want to fine-tune things to match your lines to your rods, flies and weather, this section should help you pick which line to use when.
Line length is mostly a matter of personal preference and the place where you are fishing. You may want to use a shorter line when fishing a very narrow, overgrown stream and a longer line in a river or lake.
As a starting point, though, I would suggest a line about equal to the rod length, plus about 4.5' of tippet. After you fish more, you will recognize for yourself when a shorter line or a longer line would seem to work better. Experiment with different lengths. Again, as a starting point, for extremely narrow streams, you might try a line length about 2' shorter than the rod plus 2' of tippet, so rod tip to fly equal to rod length. For rivers and lakes, perhaps a line 3' longer than the rod with about 5-6' of tippet. Please note, I have only recently realized that the 3.5' of tippet I used to recommend is actually too short. There are probably still references in the site to 3.5 feet. I will change them as I find them.
The advantages of a very short line are fewer snags on the back cast and truly excellent drifts. The disadvantage is you are much more likely to scare the fish before you get close enough to cast to them. The advantages of a long line are greater casting distance and more stealth. The disadvantages are that it is harder to keep the hi-vis line off the water (which is surprisingly important), more susceptibility to drag and having to bring the fish in by hand because you will not be able to reach it with your net. To help keep the end of the hi-vis line off the surface, it is important to lengthen the tippet as you lengthen the line. That really does help to keep the end of the line in the air.
Early in my tenkara journey, I fished with a short, simplified tapered leader between the level line and the tippet (just a foot each of 2X and 4X). When I learned that tenkara anglers in Japan tied their tippet directly to their line, I bowed to convention and dispensed with the tapered leader.
I have again started using a hand-tied tapered leader between the line and the tippet. I believe it gives better turnover of the fly, and provides a greater length of clear material, making it easier to keep the hi-vis line off the surface. The tapered leader certainly isn't as simple as just tying 4 feet or so of tippet directly to your tenkara line, but I believe it is worth the slight effort it takes to make one.
In general, I recommend level lines rather than tapered lines. The fact that they are "level" rather than "tapered" is not the issue. The difference is that most level lines used for tenkara are made from fluorocarbon, while most tapered lines are either nylon or furled from tying thread or kevlar. Fluorocarbon is denser than nylon and is thus less affected by wind resistance.
I have gotten many questions about whether you could just use any fluorocarbon line sold to bass fishermen. My answer has always been that yes, you could, but there is a substantial difference between fishing with a clear fluorocarbon designed to be invisible and a hi-vis fluorocarbon that is designed to be easy to see - which makes it easy to see subtle strikes.
There is a general consensus that furled lines are easier to cast than level lines. That is due in part to the taper (and to the physics of how a line is cast) but it is also largely do to the fact that nearly all of the furled lines are considerably heavier than level lines. Heavier lines are easier to cast.
However, lighter lines are easier to catch fish with! I would suggest anyone starting out (and any tenkara angler who fishes with a furled line) to read my essay Why Level Line for a Beginner. It won't take long to read but it could help you catch a lot more fish.
Personally, I use level lines probably 95% of the time just because they are the easiest to hold off the water's surface.
Most people who fish level lines fish fluorocarbon, but not all. There are a few who prefer nylon level line because it yields a more delicate presentation and is easier to hold off the water's surface. It is harder to cast, particularly if there is a breeze, but everything in life is a trade-off, and the best isn't always easiest.
Instructions for how to attach fluorocarbon level lines to the rod are on my Rod Care page.
Although the first tenkara lines in Japan were tapered lines,
made from twisted horsehair, most tapered lines in Japan are now made
from nylon mono or fluorocarbon. I have seen several different Japanese
tapered lines, and none of them were furled, which is how virtually all
the tapered lines available in the US are constructed. None of them were
made from tying thread or kevlar, as are the US lines.
The best I've seen are the Nissin SP Pro lines, which are made of fluorocarbon and are twisted, not furled (which sounds a bit like James Bond's "shaken, not stirred" martini). They are heavier than level lines and thus harder to hold off the surface, but many people prefer them because they are so easy to cast.
I have gotten several questions about whether you could use a regular
tapered leader sold for fly fishing. You can, but they all have one
serious disadvantage - they are very low visibility (either clear, smoke
or very light green). There are tapered lines from
Japan that are essentially the same as knotless tapered fly fishing leaders, but they are dyed a hi-vis color. They are nylon, so they do not cast as easily as fluorocarbon,
but they turn over well and do work very nicely.
Instructions for how to attach tapered lines to the rod are on my Rod Care page.
Some tenkara anglers in Japan and in the US use floating lines made from thin fly fishing running line. It is not my favorite line by any means, but I do see advantages in some situations.
When fishing still water, where drag from current is not an issue but drag from the wind blowing the line around certainly is, you might want to anchor the line in the water. Also, when fishing poppers or bass bugs (oh yes, with the right rods you can fish bass bugs) you might want a floating line. It is heavier and will turn over the bugs better than a fluorocarbon line, and it won't sink like fluorocarbon while you are letting the bug sit still.
Not just still water! I think the wind always blows in Montana and in the canyons of Colorado. Having floating line in the water anchors it, so the wind won't ruin your presentation. You will still get drag from current differentials in the stream, but that can be a much smaller problem than having the wind blow your level fluorocarbon line so badly you can barely even fish. If you fish hoppers, poppers or bass bugs, or if you fish in the west, you might want one of these in your bag.
I've also included a page on horsehair line. Despite all the latest, greatest, hi-vis, high tech lines, I really enjoy fishing with a horsehair line. It just seems to have the right density and stiffness to cast very nicely. If you would like to make your own horsehair line, the Horsehair Line page has detailed step-by-step instructions.
Horsehair lines are attached to the rod with the same method used for tapered lines.
And don't forget the tippet
which you obviously need between your tenkara line and tenkara fly. I
carry Varivas (when I can get it), which is made in Japan. Use any brand of
tippet you want, but do use a light tippet to protect the rod.
If you have any comments or suggestions, or would like to get more information about tenkara lines, please go to the contact us page.