Hi cookieman,

I'm sorry you haven't gotten any responses to this by now--I somehow missed it. A sequestering agent is a chem that will take the metals in your water and keep them in suspension, so they don't drop out and stain your pool. You might look through this thread http://www.poolforum.com/pf2/showthr...g-agent-to-use where Pooldoc discusses some specific sequestrants and where/how to get them.