Tuesday, December 4, 2018

Using Indicators and Understanding the Triangle Effect While Nymphing

In this blog post I am going to discuss the basic principles of understanding the drift, and what your flies are doing under your indicator. I haven’t fished much with an indicator this year though I do enjoy seeing the bobber go down. I'm not going to lie it is exhilarating, and is something I have loved since I was a kid. Some fly fisherman like to see a trout sip a dry fly, but I get the same excitement watching an indicator rip up stream.  It often seems to me, however, that the use of an indicator is looked down on or seen as an easier way to fish by many fly fisherman. I am not sure why there is this discontent, but I hope by the time you finish reading this article that will have a better understanding of your drift, and how to properly set up your indicator, without having to feel like you are fishing with training wheels.

My cousin Ryan with his first trout on the fly, caught using and indicator.
I agree that indicators can be an easy way to nymph fish to some extent, but if you want to be highly effective with an indicator there is a lot more to it. I think it’s actually a lot tougher than just using a longer leader with a built in sighter as with many Euronymphing set ups. Now hear me out on this, I know some of you are already typing your angry response to that statement.
In this photo I am Euronymphing for wild trout in the Allegheny Mountains of Pennsylvania.
Now the old adage of 1.5 times the water depth can get you in the ball park of the strike zone, and catch you fish, but I want to dive deeper into the world of indicator fishing. With this method, if the water is 4' deep you want to have 6’ between my indicator and flies. If the water is 3’ deep you want to have 4’-6” between indicator and flies. No doubt about it you can catch a lot of fish using that easy to use and understand formula.  I often refer to this technique to new fly anglers, but I want to help you understand what actually happens during your drift while using an indicator before breaking it down. 

A cookie cutter stocked rainbow trout caught using an indicator on a slow pool in South Central Pennsylvania.
Typically the current on top of the water will be faster than the current at the bottom. In order to not have drag on your flies you must account for this. Now we are going to break into the “Triangle Effect”, as I like to call it, that is created when using an indicator that is subject to drag.

I want you to think of your drift while indicator fishing as a right triangle. If we are looking at a cross section of a stream the top point of the triangle will be your indicator. Now let’s drop straight down from this point. This straight line distance to the stream bed is the water depth or the “adjacent leg” of the right triangle . The last point is where your nymphs are at, the ”opposite leg”. The angled line “hypotenuse” of the triangle is the depth at which you need to set your flies. 

Wow, who would have thought that you have to know geometry to nymph fish with an indicator? The simple fact is that you don’t really have to know all of these geometry terms and no I am not going to give you a formula that will give you the exact distance to set your flies. There are too many variables with to make this possible but I want to help you understand the factors that will effect the “hypotenuse” length of our triangle.

The two biggest factors that need to be considered, in my opinion, are the weight/composition of the nymph you are using and the current speed at the surface. These two factors, in my opinion, have the greatest effect on your drift while using an indicator. The construction of the indicator also plays on this, and I will touch on that in a later blog post. For the time being let’s say that we are using a 1/2” thingamabobber. 

A pretty stocked brook trout from one of my local streams.
Let’s first understand the weight/construction of our flies in relation to how fast they sink. So let’s say I am using a very buggy stonefly nymph, as seen below, tied with squirrel hair and a 3.8 mm tungsten bead. This fly will sink decently fast but the squirrel hair will slow it’s decent and experience drag in the water. Now let’s say I use a stone fly tied only with vinyl ribbing.  The synthetic fly will sink much faster and get into the strike zone faster. A common rule I use is that if the fly is dubbed or has materials that can be caught in the current, it will take a little longer to get into the strike zone. If the fly is mainly comprised of synthetics it will sink faster.

Buggy stoneflies like these will experience quite a bit of drag compared to flies tied with synthetic materials.
Have you ever wondered why peridigon nymphs are highly effective? These nymphs sink fast. They are steam lined and the fly itself is created to have very little drag while it descends through the water column. So a size 16 peridigon nymph tied with a 2.8mm tungsten bead may sink faster than the stone fly with squirrel dubbing with a 3.8 mm bead, even though the actual weight of the stone fly is much more. There are many patterns out there built to sink fast like the blow torch, seen below, as well as frenchies and many Czech nymph patterns. I don't tie with many synthetic materials as I like to use more natural materials on my flies, but I will not deny their effectiveness. Confused yet? Don’t worry, I got you on this.

Some blow torch nymphs I tied using mostly synthetic materials.
The next factor that I will discuss is current speed at the surface. The current speed at the surface is typically faster than the current speed on the stream bed. This is an important concept to grasp. We aren't fishing for bluegills on a pond while nymphing for trout. The water is moving and not just sitting there stagnant.  If you set your flies up to be just at the depth of the water they will drift above the strike zone. You can still catch fish this way, but I want to teach you how to be more effective with your indicator. When you cast upstream the instant your indicator hits the water it starts to get pulled down stream ahead of your flies. Your flies are still sinking at this point but not in the strike zone. Your main goal is to have your flies be into the strike zone before you drift past where a trout will be laying. 

Now let’s bring these two factors together in a way that makes sense with some simple principles you can remember.

Basic Principles
Fast top current- longer fly depth
Slow top current - shorter fly depth 
Slow sinking flies - longer fly depth
Fast sinking flies - shorter fly depth

Advanced Principles:
Fast top current, slow sinking flies- longer fly depth
Fast top current, fast sinking flies- shorter fly depth
Slow top current, slow sinking flies-  longer  fly depth 
Slow top current, Fast sinking flies - shorter fly depth

The longer it takes the flies to sink the longer you want to make your distance from your indicator to your flies. The more drag your indicator experiences the longer you want to make the distance to you flies. The faster the top current is the longer you want to make the distance to you flies. That’s the basics of all of it. Now let’s apply this to fishing. 

Most streams have all kinds of current, pools, differences in water depth, etc. Most of us anglers don't want to be walking up the stream and adjusting our indicator every time we encounter a different flow condition.  This is one of the reason I don't often use indicators, and the biggest downfall to using them. The easiest way to know if you are in the zone where you will receive the most strikes is to watch your indicator. If you cast up stream, and your indicator just floats on by, you are fishing too shallow.  Your flies are off of the bottom. I suggest adjusting your depth in 2" increments until your flies are just bouncing on the bottom. You will know you are in that zone when your indicator just ticks along. It should bounce a little on the drift as the flies are hitting rocks and other debris on the bottom. This is your money spot. If you go too deep your fly will keep getting hung up on the bottom, and the indicator will stop, and go under even though no fish took your flies. Just watch the indicator until it is only ticking off the bottom and you will see your strikes increase.  There are times when the trout will feed in the middle of the column, but more often than not you will see most strikes when using the method discussed above.

A golden rainbow trout I caught using an indicator an olive lively legz pheasant tail.
Another point I want to make on using an indicator is that you are not simply just casting your line and letting it lay on the water. When I am using an indicator I do everything in my power to keep my line off the water. Although I am watching the float I still want to be connected to my flies. Some instances where you have to cast a further distance, no matter what you do you have to have some line on the water. You will want to mend your line, shoot some line up stream of the indicator, so that your line does not create drag and ruin your presentation. Also when you do detect a strike, the added drag of your line ripping through the water will add time that the fish can reject your fly, or not give you enough power on the hookset. This splashing may also spook other fish in the hole.

Another shot of my cousins first trout.
I will create another post on discussing the different types of indicators, and what I like and dislike about each, but wanted to give an understanding of what actually happens on the drift, and how to set up using different flies and current conditions. Fishing with an indicator can be highly effective, and is not as simple as many make it out to be.  In my opinion there is much more to comprehend and adjust for when using an indicator effectively than when using a built in sighter, but that is just my 2 cents on the matter.


  1. This is a very well written technical nymphing article that has a high level explanation of weights reacting to current speed vs target depth in streams. I love the science behind your well thought explanations. This is my first time reading facts about the use of indicators and intelligent placement of the weighted Nymph patterns. This is well don sir.

    1. Thank you Lorenzo, your comment means a lot to me. I try to lay out things in a simple matter that the reader can pick up on.

  2. Very informative and easy to understand.Now to take that knowledge and try it out on the stream.Great job Mike always enjoy your blogs and always very helpful

  3. Where you truly see this triangle effect (e.g., the strike indicator moving downstream faster than the fly), is when you use larger nymphs such as size #4 or #6 caterpillars or large #8 sucker spawn.

  4. Great post! I like how you touched on the key point about being in the zone. The goal is to keep the flies in front of the fishes eyes so it can see them and take the fly. Also I like that you touched on the fact that the water in the zone is much slower than the water at the top of the river.

    1. Thanks Trevor. A lot of new anglers set it up like they are fishing for blue gills. I really noticed a huge increase in takes when my indicator ticks along. There are times where they may be feeding mid water column but more often a mid column feeding fish will swim down to take a fly before one lower in the column will swim up. That’s just my experience with it though.

  5. Thanks for posting. I am new to fly fishing and have been experimenting with this. I have seen exactly what you are talking about. That "ticking" are the nymphs bouncing. I always get more hits when in that zone. Question...thoughts on split shot sinkers in this equation?

  6. I suggest using tungsten bead nymphs. I use a lot of anchor nymphs to get down. 3.8mm beads and sometimes weighted bodies. Tungsten is your friend here. I always fish with tandem rigs. I haven’t messed with it but drop shooting would seem to help keep you connected to the flies more than a split shot above or between the flies.

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