Nifty on Tuesday ended 238 points lower to sneak below its 50-DEMA for the first time in the last four months and form a long bear candle on the daily chart. The overall chart pattern of Nifty is weak. The next lower levels to be watched are around 21,500 in the next one week. Any rise up to 22,000 could be a sell-on-rise opportunity, Nagaraj Shetti of HDFC Securities said.