Heavily weighted patterns are necessary in order to get a fly down on the bottom to reach the feeding zone of many roughfish species, especially in riffle/heavy flow areas. Look for flies weighted with tungsten beads or heavy gauge wire bodes. A minimum of 2X strong hooks are required; these fish will straighten hooks. Heavily weighted trout nymphs will work for most situations, especially if you do not have access to specialty carp and roughfish flies. Better yet, tie your own to get the job done right.
Effective pattern sizes when fishing for suckers range from size 8 to 14. Traditional nymph patterns are money. I like tying patterns on short shanked hooks with large hook gapes like an egg hook or scud hook. By upsizing the hook size with the shorter shank, you are still able to tie a pattern in its normal proportion, but the wider hook gape will greatly increase your chances of hooking up with a fish.
For carp, rubber legged flies, crawfish patterns, wooly buggers, and specialty patterns like the San Juan Worm, Darth Clam, Carp Carrot, and Swimming Nymph are deadly. I prefer to have each of these patterns tied in different densities and weights, dependent on the environment fished, depth, and rate of flow. Some locales may require a fly to get down deep, fast. Other situations may dictate a fly to hold in “the zone” for as long as possible. Lightweight flies with small profiles are necessary when delicate presentations are required for weary fish in skinny water. Due to the fickle nature of these fish, it is best to come prepared with an arsenal of patterns.