Wow, Hopefully somone on here knows because I've never seen this in any of my tanks. That would bug the heck out of me though!! Have you had this problem for a while?
Chrysophytes grow in freshwater, so to be more specific what you have there is Silicoflagellates. You would battle them the same way that you would dinoflagellates.
Here is a thread where I addressed this problem recently. You can link the sites listed. It's a tough one and it looks like you've got it bad so get hot on it right away. If possible I'd remove your live animals for a few days while you battle it.