Last summer's Oni School was an eye opener for me. I had always thought that Tenkara no Oni fished with light lines, and the lighter the better. The weather was quite windy during the school, though, and he mostly fished size 4.5 lines. Before the school, Erik Ostrander had told people to bring lines of different weights. I did, but nothing as heavy as a 4.5. With that wind, to be able to cast I had to beg some line from Oni himself.
This past Sunday I got another eye opener. I had known for a long time that the different colors of level fluorocarbon tenkara line were all quite visible in good light, but there were times when one color was more visible than the others. It had been a long time, though, since it really hit home.
I started out on a stream where I have caught fish in the winter. On Sunday, I managed to catch one fish, which is about normal for me in winter. One fish is a nice day, two makes it stellar. I've never had a "many" day in the winter.
After cherry-picking the best spots (on that stream in the winter, fish seem to reside only in the deeper pools) and still having some daylight left, I decided to go exploring. I found a stream I had fished once with Coach years ago (in a different spot) and even better found some nice looking water where there was public access.
By then, though, the light was starting to fade and I was starting to have a very hard time seeing the orange Sunline. I guess by now it's been quite a few weeks ago, but last fall I had compared lines from size 1.5 all the way up with the TenkaraBum 36 and 33. The size 1.5 and 2 were left over from when Sunline sold a bright orange salt water line, which they discontinued just before introducing a bright orange tenkara line. Since I had all the orange lines in my vest, that is what I had been fishing.
The bottom of the stream I was fishing is rocky, and the rocks are primarily a brownish orange color. The woods in the background were carpeted in brown leaves. In the fading light it got very hard to see the orange line. After thoroughly searching all the pockets in my vest I found one Yamatoyo line. The chartreuse was completely different from the background colors and was easily visible. I didn't catch any fish, but at least with the Yamatoyo I was sure I wasn't getting any hits.
Early on, when going to a fly fishing show and talking to people who were buying their first tenkara rod, I generally recommended that they buy two different lines, at that time a size 3 and size 4 Sunline. My thinking then was that the size 4 was for when they were just starting out and also later on when there was a bit of a breeze. The size 3 was the line to work towards and to use on a still day.
I gradually stopped that, and recommended just the lightest line that a beginner could reasonably cast with any given rod. I now think I should go back to recommending more than one line. The experience at the Oni School clearly proved that having a heavier line for a windy day is a good idea. You might choose to stay home and tie flies on a windy day, but if you are on a multi-day trip away from home you'll probably want to fish anyway.
I am beginning to think I should recommend that people buy lines of different colors in addition to different sizes. All are quite visible in good light, but there are conditions when any one of the three colors (orange, pink or chartreuse) is very hard to see and one of the others is much more visible.
Fluorocarbon tenkara line isn't exactly cheap, which is why I haven't recommended multiple lines all along, but on the other hand, none of us get to fish as often as we'd like, so having a line that "saves the day" is probably worth it (and probably cheaper than the gas it took to get you to the stream anyway).
I guess where I come out on the question now is this: If you want to save money, buy one, any one. If you want to save a trip, buy at least two and maybe all three colors (and at least two different sizes - each).