Depends on the size of trout I am after, and the type of water I'm fishing. I usually go with 6lb for all around stream fishing.

4lb. on one ultralight, 6lb. on 2 others.

i prefer the 22# braided when fly casting

4-pound Stren Original mono in green.

I prefer 8 lb. braided (Fireline) a simple flick of the wrist and they are hooked. plus it casts quite a bit further than mono.

Since we mostly fish rivers and streams filled with rocks my son and I prefer 6 pound mono. I have used various brands and colors and don't really prefer one over the other. That Fireline fishinfool suggested sounds interesting, I'll look at it.

6lb green mono.

4 pound mono on an ultralight rod and reel.

I use 4lb Trilene Sensation.

i use a mono 8lbs test line. i caught 5trout in 2 days and all were 15+ inches. one was also 27.5inches!!!!

I used to stream spin fish for trout exclusively with 4# mono. Moved to ultralight about 40 yrs ago using clear 2# Garcia Platyl line on an Alcedo Micron. Still have a couple spools of 3/4# (that's three quarter pound!!) test Platyl!! Been searching for a replacement ever since they stopped making Platyl. Fished several years with green Maxima, then used clear Andre for many, many years -- all 2# test. When fluoro came out, used 2# test Vanish and liked it until I began having trouble seeing my line. Tried Vanish Transition gold, but didn't see much difference. Would like to try Vanish Transition red, but appears they don't make it in 2#. Will be trying some 2# P-line CX Premium, clear flourescent, but don't hold a lot of hope of increased visibility to me because I think the visibilty advantage of the flourescent is with a black light. Might have to go back to a more colored line in 2# -- either mono, fluoro, or fluoro coated, but would like to stay away from too much color because I don't like to use a leader.

If I begin to lose a lot of fish or fish a river where 16 to 18 inchers are regularly expected, I move up to 4#, still using ultralight rod and reel. I've gotten me some 4# Vanish Transition red to try.

For big, fast water canyon fishing, where fish up to 5 lbs or more are expected, I gone to 8# flouro (Cabela's No-Vis) Used to use 8# Magnathin. Have picked up some 8# Vanish Transition red to try on my next trip.

I think I do have more tangles since going to fluoro, but not sure how much is due to fluoro and how much to the reel. Most of my mono fishing was done with the old style, short, unskirted spool reels while most of my fluoro has been with the longer, skirted spool reels. Most of my tangles are when the line loops back and wraps in the area between the rotating bail mechanism and the body. The rotating bail cup a short unskirted spool is in, prevents the line from doing this. I have less tangle problems involving the line coming off the spool and looping with the unskirted spool reels whether mono or fluoro.

The smaller diameter the more fish you will catch. Lighter line is harder to see and the bait or lure acts more natural. I go with 6 lb mono

The lighter the line the better because it is less easier for the fish to see it, but if you go too light, the fish can break off. The line I use is 6-10 lb mono, depending on the size of fish I am going for.

i am a huge fan of 4 pound floro on an ultra light rig, i got into a big old brown the last time i was in the stream that was a fun fight!