I have out west but not here in the ns. But the same thing goes everywhere for nymphs, can't beat natural colors. olives blacks browns tans will work under the right conditions. Czech nymps are usually caddis immitations and the czech nymphing comes from the style or way of fishing, not so much the style of fly, but more the way the flies are presented and fished with a short line. Kind of a short lined high sticking presentation. In places that are allowed multiple flies such as 3, the bottom fly is the most exact representation of the caddis/nymph, the middle fly is usually the heaviest with a touch of color like pink or red. Many diff nymphs can be used but must be weighted somehow either with lead or beeds. Ur usually in some faster water trying to hide urself (ur basically right on top of the fish using these techniques) so u need the extra weight to get ur flies down fast as theres only a small amount of line to fish with and theres a shorter drift time as well fishing this way. Hope this helps. Had a friend out west that fished this way quite a bit and i tagged along with him a few times. This technique deff works, more for him than me, but i picked his brain alot.