What is the main difference between pole floats for rivers compared with stillwaters?
Very much the same as for running line floats. For instance, pole floats for river fishing will typically have a roundish body placed towards the top of the float. Indeed, in strong currents it may be totally round to make it easy to 'hold back' the tackle, so that the bait attractively rises up in the water.
On stillwaters, you won't be holding back, so the body of the float will be slimmer. This means that it comes out of the water cleanly on the strike. The body is likely to be pear-shaped with the slimmest part at the top, which helps detects lift bites i.e. when the float rises as the fish lifts a shot in the water.
I went to a well stocked stillwater recently to fish for Roach. Despite the conditions looking good, no-one was catching. How would you feed in these circumstances?
Feeding is one of the most important factors in sorting out the men from the boys. In this particular case, I'd feed much more sparingly than usual and hope to build the swim up for later in the session. The key is to loose-feed little and often, perhaps with a very small amount of fine groundbait. However, don't put any feed in before you start fishing and, even then, feed just half a dozen or so maggots at a time, every 2-3 minutes.
Also, start by fishing on the bottom and keep the bait moving about in order to try to induce a take. Good luck!