A DE filter will be clogged quickly by live algae. Kill the algae first with shocking the pool and then let your filter work to filter it out.

Your CH is pretty high. I would suggest not using any cal-hypo in your pool.

Add the CYA to an old sock and hang it in front of the return jet. That way it will not be backwashed out. Every now and then give the sock a squeeze to help it dissolve faster. Two pounds will only add another 20ppm of CYA for a total of 32 in your pool (if the 12 is right). You may end up deciding to take it just a little higher. We usually suggest 40-50. But, you can decide that later. See how the amount you are adding now works for your pool.

It is best if you test your own water. You'll usually get more reliable results than you'll get from a pool store. The kit we recommend is the Taylor K-2006 or 2006C (same kit, larger bottle of some reagents). If you buy it through the Amazon link in my signature, the Pool Forum makes a little money on the sale which helps us keep this form online. Only buy if the seller is Amato Industries, however. Some other sellers are substituting the K-2005 which you do NOT want. If Amato isn't listed, wait a day or two and try again. They seem to restock pretty quickly when they sell out.

A request from us: Make a signature line. To make it easier for us to help, if people will create a signature line with their pool specs, it keeps us from having to reread through posts to find out basic information. You can create a signature by clicking on 'settings' in the upper right-hand corner of the homepage. In your sig, please put type of pool, volume, type of filter, size of pump, whether or not you have a SWCG or any water features and the fact that you do or do not have a K-2006. Thanks!