Building a Fly Box for the South Platte — What's Actually in Mine

Most fly boxes I’ve ever seen are graveyards. A hundred patterns stuffed in, mostly bought in panic at fly shops before a trip, ninety of them never tied on. The box gets heavier every year and the actual fishing happens with the same six flies.

Mine is the opposite. After fishing the South Platte 80-plus days a year for long enough to notice, I’ve trimmed my main box down to the patterns that actually earn their space. The rest live in a backup at home, occasionally rotating in when something specific demands it.

Here’s exactly what’s in the box I open at Deckers.

The Box Itself

Umpqua UPG HD Medium Foam. Slit foam top and bottom, magnetic closure that hasn’t failed, hinge that doesn’t snap when frozen. I’ve owned three over the years; the current one has visible thumb-grease wear and that’s the way I want it. Buy once, cry once. It lives in the chest pocket of the Umpqua Overlook 500 and gets unloaded into a spare box in the truck at the end of each season.

The medium is the right size. Large is too much; you can’t see what you have. Small is too little; you run out of room for the backups. Medium is the sweet spot for tailwater fishing.

Section 1 — Heavy Nymphs (the Point Fly Pile)

This is the busiest section in the box. The point fly is the workhorse and gets cycled hardest.

• Olsen’s Blowtorch — orange tag, sizes #16, #18, #20. My favorite fly. The orange-tag version handles stained water and high flows. It’s the first fly I tie on most days. I lean small — #18 and #20 see as much water as the #16.
• Olsen’s Blowtorch — green tag, sizes #16, #18, #20. Same fly, clear-water variant. When the water drops and clears, the orange tag becomes too loud and the green tag earns the point spot. Smaller sizes (#18, #20) are technical-water defaults on Deckers.
• Duracell Jig — sizes #16, #18, #20. When the Blowtorch isn’t moving fish, the Duracell is the swap. Heavier in the head, slightly different profile, occasionally outfishes everything else for reasons I can’t fully explain. I go up to #20 for technical fish.
• Walt’s Worm — sizes #14, #16, #18, #20. The cold-and-slow specialist. When the water temps drop and the fish are sluggish in the soft water, the Walt’s Worm in natural tan or olive earns its place. Small variants (#18, #20) for pressured Deckers fish.
• Frenchie — sizes #16, #18, #20. The third-choice point fly. Slimmer profile than the Blowtorch or Duracell. Works in technical riffles where bulk silhouettes spook fish. The smaller sizes (#18, #20) are the ones I reach for most.
• Spanish Perdigon — sizes #16, #18, #20. When a BWO hatch is on but the fish are still subsurface, the Perdigon’s slim silhouette imitates the emerger sinking back to the bottom. #20 is the tail-end-of-hatch size.
• San Juan Worm — red, pink, and purple, sizes #14, #16, #18. I fish worms all the time. They’re not glamorous and you won’t see them in Instagram fly boxes, but a red SJW in high or stained water is one of the most consistent producers on the South Platte. Post-runoff, post-rain, any time the water carries extra color, the worm earns the point spot. Pink works in clearer water when red feels too loud. Purple is the wildcard — it shouldn’t work, but it does, especially in low light and overcast water. #18 in any of the three colors is the technical-water variant when fish are pressured and a thicker profile gets refused. (No #12 — anything that big telegraphs too obviously on the Platte even in chocolate-milk water.)
• Egg patterns — sizes #14, #16, #18, in season. Brown trout spawn at Deckers runs October into November, rainbow spawn comes in March and April, and during both windows the eggs become the most-eaten food in the drop zones. I lean smaller than most anglers do here — #18 eggs get refused less. Trailing fish behind spawning beds get fat on dropped eggs. I run pink, peach, and chartreuse Otter’s Eggs and Y2Ks, plus a few dead-egg (washed-out cream) variants for the tail end of the spawn when fish have seen everything bright. Fished as a point fly with a small midge or RS2 dropper. Pulled from the box outside spawn windows — there’s no reason to drift eggs in July.

Quantity ratio: More Blowtorches than anything else by a wide margin. If I lose one, I’m not skipping a beat.

My take: A good fly box should embarrass you a little with how repetitive it is. If a stranger opened mine and said “this is just a hundred Blowtorches and a pile of midges,” they’d be mostly right — and that’s exactly the point. The graveyard boxes are the ones with one of everything and confidence in nothing.

Section 2 — Light Nymphs & Emergers (the Dropper Pile)

The dropper rides 18–24 inches behind the point. Lighter, smaller, usually the fly the fish actually want.

• RS2 — sizes #18, #20, #22. The universal dropper. Grey, olive, and black variants, but mostly grey. When the BWOs are coming off, this is the dropper.
• Barr’s Emerger (Flashback) — sizes #18, #20. Brown and olive variants for BWO and PMD respectively. Sits in the surface film vs. the RS2’s deeper drift, so they cover different parts of the column.
• Mercury Black Beauty — sizes #20, #22. Tied with a silver bead instead of black, which catches just enough light to trigger eats when fish are looking for sparkle.

Section 3 — Midges

Midges are 60% of what’s hatching at Deckers in any given month, especially October through April. This is its own section because they’re tiny and need their own real estate.

• Zebra Midge — black thread / silver wire, sizes #18, #20, #22. The universal. If I had to fish with one midge for the rest of my life, this is it.
• Zebra Midge — red thread / copper wire, sizes #20, #22. Winter blood midge. January through March, this is the one.
• Zebra Midge — olive thread / copper wire, sizes #20, #22. Spring transitional. Less critical than the other two but worth having when the water warms in late April.

Section 4 — Dries

Smaller section because I’m a nymph-dominant angler. But the dry-fly window matters when it matters.

• Parachute Adams — sizes #16, #18, #20. The cheat code. When you can’t identify what’s hatching but the fish are eating something on top, the Parachute Adams gets you in the game.
• Sparkle Dun BWO — sizes #18, #20, #22. The South Platte BWO hatch is one of the most reliable in Colorado. The Sparkle Dun fishes the emerger and dun stages without needing to change patterns.
• Parachute PMD — sizes #16, #18. PMD hatches start mid-April on Deckers, peak in June. Pale yellow body, white wing post for visibility.
• Elk Hair Caddis — sizes #14, #16. Caddis season at Deckers runs May through September. Tan and olive variants.
• Stimulator — size #14. A search pattern when nothing else is working. Big and floaty enough to act as an indicator for a dropper, attractor enough to pull fish up.

Section 5 — Streamers

Streamers are a different kit on a different rod (Redington Vice 7wt + Lamson Liquid S). They don’t live in this box. They live in a dedicated streamer wallet in the truck kit. That said, I’ll keep a few small streamers in the main box for opportunistic moments:

• Wooly Bugger — size #10, olive and black. When a fish refuses everything you’ve tried, a small bugger swung past it is sometimes the answer.
• Mayer’s Mini Leech Jig — sizes #12, #14. Black and olive (olive #14 is the workhorse). Small enough to fish as a dropper behind a heavy nymph if a streamer-style approach is called for in nymph water.

What’s NOT in the Box

Just as informative as what’s in there:

• Terrestrials (hoppers, ants, beetles, Chubby Chernobyl). Not because they don’t work here — they absolutely do once summer arrives. They just don’t belong in the year-round box. From late June into September I add a separate terrestrial rotation; a Chubby Chernobyl in #12–14 becomes a real searching pattern and the trout will move for it. But that’s a summer-only kit — the box you’re reading about here is the nymph-and-midge engine that runs the other nine months.
• Heavy stonefly nymphs (big Pat’s Rubber Legs and friends). The South Platte doesn’t carry the stonefly biomass of a freestone like the Eagle or the Gunnison, so the chunky rubber-legs stuff mostly gathers dust here. Save it for the rivers that grow them.
• Wooly Bugger in large sizes (above #8). Lives in the streamer wallet, not the main box.
• Sculpins, articulated streamers, big stuff. Same — streamer wallet, dedicated rod, dedicated day.

Frequently asked questions

How many flies do you actually carry in the main box? Fewer than you’d think — maybe 150 across all the sections, and the ratio is wildly lopsided toward Blowtorches, Zebra Midges, and RS2s. The rest are there for the one specific day that demands them.

What’s the most important nymph size for the South Platte? Small. I lean #18 and #20 for most point flies and #20–22 for midges and droppers. These are pressured tailwater fish — when in doubt, drop a size, not add one.

Do I really need three colors of Zebra Midge? On this river, yes. Midges are ~60% of what’s hatching most months (October–April). Black is the everyday, red is the winter blood midge (January–March), and olive is the spring transitional. They’re genuinely different days, not just different threads.

If you could keep only one fly, what is it? An Olsen’s Blowtorch, #18. It’s my favorite fly, the first thing I tie on most days, and the one I’d actually be nervous to run out of. Everything else is supporting cast.

The Backup Box

A duplicate of everything above lives in a dry bag in the truck. When you drop the pack box in the river — and you eventually will — this is the backup.

The Ratio That Actually Matters

Of every 100 flies I tie on in a season:

• 40 are Blowtorches (orange or green tag depending on water)
• 20 are Zebra Midges (color depending on month)
• 15 are RS2s
• 10 are Walt’s Worms or Duracell Jigs
• 8 are Perdigons or Frenchies
• 5 are dries (Sparkle Dun, Parachute Adams, Elk Hair Caddis)
• 2 are streamers (Bugger or Mini Leech)

That ratio is what the box reflects. Stock the patterns you actually fish — not the patterns the fly shop says you should fish.

You can stock most of these through The Fly Fishing Place — use code RDC at checkout. They carry the Blowtorch, Walt’s Worm, RS2, and Zebra Midge in the sizes that work for the South Platte.