I have only been to Haidian swimming pool, it's on Yiheyuan Road. ￥19 with yacol card. It's very crowded and the service is not very good.
Maybe you can try Hosafitness, it has a few chain stores in Haidian. I know there is one at Jinqiu jiayuan community, Zhichun Road. This one is a bit expensive, but if you have yacol card, it would be around ￥35.