There are no hard and fast rules about the “best” way to fish the Cod Beck. Our members seem to employ many different succesful methods. It’s perhaps better to approach it in a style or manner you feel comfortable with, rather than listen to too much hard-core advice that may, or may not, extract you an extra fish or two on the day.
Perhaps some generalisation is in order.
It’s a small beck and quite overgrown in parts, so wading tends to be the order of the day for most, but not all, stretches. I would say that chest waders are essential, although some say they get by fine with hip or belly waders. I’ve shipped enough water over the top of my chesties in some parts of the beck to not recommend anything else. But use what you want, but be careful, there are some surprisingly deep slippery sections in places.
I think stealth whilst wading is very important. Take it slowly and carefully whilst getting into position. It’s surprising just how close you can get to fish if you use a little caution. Particularly avoid creating upstream surges of ripples into the pool ahead of you. On the plus side wind and ruffled water help disguise your movement from any fish ahead or below of you, although it can also hide the whereabouts of the fish from you!
People have many preferences for rod length and weight, but generally anything around or under 8ft and between 3-5 wt is fine. However, if there is any breeze blowing, and there often is, a three weight can be a little under-assertive in those conditions. Double taper or weight forward lines, take your pick, whatever you are happiest with.
Contrary to popular thought, I fish short leaders, rarely more than 7-8 ft in length. Personally I find trying to manage longer leaders in the conditions of the Cod Beck just too demanding on my limited casting ability. But you should use whatever length you think appropriate and if you can manage longer leaders , then great. I know some people recommend 14ft ones!
One thing you will need to develop, if you want to fish every bit of the Beck, is a wide variety of casts. Overhead, side, roll, upstream reach, steeple, bow and arrow and many others that are simply un-repeatable one offs that change hourly depending on your relative position, beck wise, to the rising trout. This is not a manicured chalk stream, it’s a Wild Brown Trout river. Get used to losing flies!
I’m often dismayed how the surrounding flora can make it so difficult to cast accurately to rising fish and I’m just as often amazed when I pull it off. Sometimes I don’t care about hooking the fish (although it helps), just covering the fish with a difficult cast can constitute a major success.
Thankfully, most of the Beck is not like this, there are many stretches where you don’t have to thread your back cast through overhanging branches and cast round corners. Probably well over half of it!
Generally the fish are quite free rising and usually don’t seem to be too fussy about fly selection, taking a wide variety of imitations. Two good general approaches are to simply fish a searching dry-fly, or to fish what is colloquially known as the “Klink and Dink”. This is a style of fishing popularised in New Zealand of fishing a dry-fly with a nymph attached underneath. On the Beck this is usually a Klinkhammer (#14-16) and a weighted Pheasants tail nymph / Gold ribbed Hares Ear (#14-18), but vary this as you wish. Some fish with the dry-fly attached via a dropper on the leader and some fish with the nymph tied directly from the bend of the dry. Use whatever you are happiest with.
The “Klink and Dink” approach gives the best of both worlds and allows you to determine if they after a nymph or a dry-fly on the day. In my experience it’s often, but not always, a mixture of both!
We tend to get mixed hatches with several species emerging, egg laying, dying or rising to the surface all in the same day and often at the same time! A possible reason for the apparent lack of fussiness, as the trout and grayling are used to taking whatever is available.
We usually have a reasonable mayfly hatch, not a blizzard of them flying around, but enough float downstream to turn the heads of some of the largest (and smallest) trout. It really pays to keep your eyes open and see what is going on.
A tip if nothing is working is to fish a small (16-20#) black dry-fly, Black Gnat, Klinkhammer or the like. There are a lot of black flies around the Beck, particularly around the hawthorn bushes, although they don’t seem to be the classic Hawthorn fly. The fish seem to like them and I’ve risen fish from stretches where there wasn’t a single rise form.
Perhaps the best bit of general advice I can give, is that you should simply relax unwind and enjoy it.